System: Pumps, Relays
Maintenance FAQ for 7xx/9xx/90 Cars
Pump and FI Relay Diagnostic Tests. Here is a procedure to test
the operation of the fuel injection relay and the operation of both fuel
pumps. The 3 main things to check in the fuel circuit are the fuel
pump relay, and the 2 fuel pumps.
1. Fuel Injection Relay Test.
There are 2 relays inside the fuel injection/pump relay. One of them should
turn ON when the ignition is turned on (without turning over the engine),
and the other relay (which actually turns the fuel pumps) should come ON
when the engine turns over/runs. You can check the 1st relay by putting
your fingers on the relay module and turning the ignition on and off repeatedly.
You should feel the relay click on every time. If it doesn't, that relay
isn't working. And you'll find the car doesn't start if the relay did not
2. Fuel Pump Diagnostic Tests.
On the 740, the fuse-box + relay box can be pulled out a little to facilitate
inserting/removing relay modules. So pull it out as much as the wires will
allow. Pull out the fuel injection/pump relay module. Now take a small
piece of wire to jumper terminals 30 and 87/2 on the relay board (the terminals
are identified on the relay module pins. The 2 terminals are the nearest
left and middle right pins on the relay board). This should make the car
act like the fuel pump relay is ON.
Now turn the ignition ON (without turning
the engine). You should hear a whirring sound right from where you are.
That will be the main fuel pump. Now go to the gas tank and unscrew the
cap. Put you ear to the hole and you should hear a smaller whirring sound.
Or, listen with a piece of heater hose to the tank pump through the gas
filler with car running. Should hear a humming. That will be the in-tank
pump. If you hear both noises, the fuel pumps should be OK.
CAVEAT: The main fuel pump is not designed
to be run without the in-tank pump "on", so get the second part of this
test over quickly. You should not need to keep it running in this
condition for more than a few seconds to complete this part anyway.
To check the pumps individually, you can
pull out the in-tank fuel pump fuse after you do the above test, and repeat
the test. You should not hear any whirring at the tank, but you should
be able to hear the main pump.
of Bad Pump Relay. [Symptoms:] 89 740 died & started 10 min. later.
My '89 740 did the EXACT same thing for a while. When it acted up it did
have spark. It seemed to be related to getting hot. It would die in motion,
or when hot, it would also refuse to restart 'til it rested for 10 min.
As far as driving it, not much you can do, just be prepared to pull over
and give it a rest for 10 min. When it acts up, as the key is turned "ON",
listen, the fuel pump should normally be heard to come on for about 1.5
sec. If it's not coming on, I'd bet on the relay. [Diagnosis:] After replacing
the fuel pump relay ($38 at dealer), it's been 100% fine. [Editor's Note:
See the note on "Headlamp Circuits/Relay Won't Function" in the Electrical:
Lighting section for more relay information.]
Pre-Pump Problems. [From RPR ;
illustration copyright and used by permission:] 7xx/9xx Volvos are fitted
with a fuel pump inside the fuel tank. This pre-pump, also called a primary
or feed pump, moves the fuel out of the fuel tank to the main fuel pump.
This prevents fuel starvation problems that may occur when the tank is
less than half full. If the main pump has failed, the car will not run.
If the pre-pump is inoperative, you'll have fuel starvation
symptoms. These may include hard starting, louder than normal main fuel
pump noise and a loss of power under load. To check the operation of the
pre-pump without removing it from the tank, locate the pre-pump fuse. Remove
this fuse with the car idling. You should be able to detect increased noise
from the main pump and decreased vibration of the fuel tank itself.
[Diagnosis of pre-pump: Are there any short
cuts to check to see if the in tank pump fuel pump is working? I opened
the gas cap and did not hear any noise.] You should really be able to hear
a "buzzing" sound in the fuel tank if the in-tank pump is running. Sometimes
a length of heater hose inserted in the filler neck and placed against
your ear will help isolate the sound. Try it with the fuse in place and
removed and listen for a change in the sound. You might also find another
Volvo owner who might let you probe their filler neck with your length
of hose and listen to their in-tank pump . Assuming their in-tank pump
is working you would be able to determine the sound you are listening for.
If you do take it out of the tank:
Replace the short segment of rubber hose
with a new section of fuel hose.
[Symptoms of worn fuel pre-pump:] My experience
with a worn fuel pre-pump is that it will cause the engine to miss and
lose power under conditions of high flow (high throttle and high rpm).
The problem grew worse very gradually (over 10's of 1000's of kms). It
certainly wasn't going to leave me stranded anywhere. [Another example:]
My wife drives an '83 760, which I have maintained as needed. Recently,
the car started to vapor-lock in warmer weather, and/or when the fuel level
dropped to around a 1/4 tank or lower. Oddly enough, when I refill
the tank, the problem seems to go away. [Test Tip:] As far as a definitive
test goes, I guess it would be necessary to set up a pressure gauge and
flow meter as well as a valve in the circuit that would allow a specified
volume to flow while reading pressure, but see the above fuse and noise
procedure for an alternative.
Replace the "sock" that is on the end
of the pickup tube (about $15 from Volvo)
DO NOT bench test the in-tank pump. When
the pump is removed from the tank arcing will occur when powered up and
can result in a fire due to the gasoline vapors present. Certainly don't
remove the pump from the fuel level in the tank and give it a quick bump
on the starter to check out its function- that can result in one hell of
a fire (and explosion). The pumps are designed to run submerged in gasoline.
[Car Stalls During Turn: Fuel Prepump Failing.]
[Query:] I bought a used '87 760t. It ran fine when I first got it but
after a few months it started stalling when making a left turn. Not every
time, but its worse (more likely to stall) if I'm decelerating, in fact
I can usually avoid the stall if I slow down before the turn and then give
it some gas during the turn. When it does stall it almost always starts
right back up no problem. [Response: MikeW] The stalling during turns
is usually indicative of a problem with the in-tank fuel pump. Does it
happen when you have a full tank of gas, or only when your down around
1/3 tank or less? Anyway, it sounds like your in-tank pump may be bad,
or the rubber hose connecting it with the metal line running out of the
tank may have deteriorated, or the filter sock on the bottom of the in-tank
pump is plugged.
Pump Noise. Fuel Pump Noise. [Query:] My car is running perfectly
but whenever the fuel-gauge drops to around 25%, noises coming out unexpectedly,
but after refuelling the noise will suddenly disappear. Does anyone
could tell me what's wrong with my car? [Response 1: Michael Pardee]
Sounds like the hose on the in-tank fuel pump has a hole in it. That is
very common, and if the hole gets much worse, it will not be able to run
below 1/4 tank at all. Fortunately, it's an easy fix. [Response 2:
Peter James] I would agree with that and/or the intank pump has failed
and you are
now stressing the main pump, which in
turn can lead to premature failure of the main pump.
[Response 3:] Are you sure it's the in-tank
pump, not the main pump down by the rear wheel arch that is making the
noise? Most commonly this pump makes this noise not because it is failing,
but because the in tank pump is not supplying the fuel to it for some reason.
It won't do it any good to operate in this condition, and when the main
pump fails, you're stuck at the roadside. The most common causes of in
tank pump woes are not failure of the pump itself, but two other possibilities:
The little sock filter on the in tank
pump intake is blocked with debris
Both require the pump removed from the tank
to rectify unfortunately.
The pipe from the in tank pump has split.
Main Pump Problems. [Symptoms of dead main fuel pump:] car won't run.
Pour some fuel into the inlet manifold
or use ether quickstart. If the motor fires and runs for a second or two
then dies, then your electrics are OK but motor will not rev as there seems
to be no fuel.
If you can't wait or have no cash, your
can cut your old line off and move the accumulator about 1.5 inches forward
on the new pump. Then take off the old pump, (Three bolts its in a cradle,
13 mm I think)
Next, you could replace (or use a spare)
the fuel pump relay. Normally, when you switch on the ignition, but just
before you actually crank it over, you should hear the fuel pump working,
(a faint whine) then it stops (i.e. it is priming the system to pressure)
If you hear nothing at all, then the relay could be bad (it is a green
bastard stuck in the row of relays (usually top left as you look at it)
behind the ash tray. You should remove the little shelf panel to get at
Another thing you can do is undo slightly
one of the unions in the fuel distributor, using a 12 (or 13mm) mm ring
spanner. Normally, undoing one of these, there will be a spurt of fuel.
If there is nothing, you have no fuel pressure.
So far it could be the relay or the main
pump. You could buy a new relay, slot it in and the car should go. If not,
then it is your main fuel pump (or pump wiring, but that is less likely,
as the connections to the pump are very solid and durable) You could disconnect
the pump wires (you can do this without removing it completely) and get
someone to crank while you test voltage across the connectors.
If you have an old relay, you can 'short'
it by levering it out of its box and disconnecting the little springs in
it. As soon as you put it in (even without the ignition on) the main fuel
pump should start to run and keep running and car should start. If nothing
happens, then your main pump is well dead. Don't forget to remove the relay
and chuck it, or mark on it what you did to it as it would be really dangerous
to use otherwise. It is a strictly 'get you home' or diagnostic.
So it's your main fuel pump. The tank
pre-pump can be dead (or dying) and the motor will still run if you have
more than half a tank of fuel. Get a new one if you can, or a scrap
one from a yard, but test it before you buy it. Order the piece of fuel
line from the accumulator to beginning or main engine line from Volvo.
Then disconnect the engine end first as
it will be dry. The tank end will spill, so have the new pump ready in
position. Cut the old clip off with a hacksaw and use a jubilee clip or
whatever equivalent screw clip. Pull the old pump off, whizz the new one
on and tighten the clip not too much. Then bolt the pump onto the car.
Then push the new tubing onto the accumulator or the old piece on. Its
best to buy the new piece. Although it is a pain to undo the union of the
short piece with the engine line.
Don't even think of trying to change the
tank pump as it is a nightmare if you don't like confined spaces. Also,
it is a killer to get the auxiliary tank back on.
Check Valve. [Symptom:] My '84 244GLE is equipped with B23F engine
and LH Jetronic 2 fuel injection, she doesn't want to start (read run)
the first time -though cranks fine- when it has been sitting at least 6
hours. The car will start without hesitation on the second try. [Diagnosis:]
It sounds like a classic case of failed fuel pump check valve, on the main
pump under the car, left side, just ahead and inboard of the left rear
wheel. They cost about $14 at the dealer and are fairly easy to install.
Just go buy one at the dealer and they'll show you in the parts book where
Outlet Hose. Don't let those guys charge you $200.00 for working on
your pre-pump! Most likely the small piece of rubber fuel line between
the in-tank electric pre-pump and the metal output tube has eroded and
needs replacing. This is not a difficult job but requires getting under
the car to detach the pre-pump output line from the main fuel pump inlet
hose. Then the rest of the pre-pump removal can be done from inside the
Fuel Tank Line Clamp Recommendations.
[Query:] Which clamps work best on fuel lines inside tanks? What's
their projected life span ? [Response: Jim McDonald] Breeze clamps;
about 250 years if you get all stainless ones, somewhat less in plain steel.
Pressure Regulator and System Pressure. What about the pressure regulator
concept? Very unlikely. But I'll give you good advice, install an in-line
fuel pressure gauge (liquid filled). It'll save you from guessing on your
problem as to fuel pressure and clogged lines or filter. I've got mine
from Summit part #SUM-800160 (60psi) $19.95.
[Symptom: Car won't start] I hooked up
a fuel pressure gauge and found that no more than 10 psi was generated
while running the fuel pump continuously, and the trickle sound got worse.
I removed the vacuum hose from the fuel pressure regulator, and found a
couple of drops of gas. Just as a check, I turned the fuel pump on for
one more second....YEOW!! I could have burned down the whole house with
the stream that shot out the front of the regulator. Conclusion: No pressure
to injectors, but plenty of raw gas supplied to the intake manifold, thence
to the cylinders, and finally onto the ground under the exhaust manifold.
No wonder the car wouldn't start. I have a new fuel pressure regulator
Fuel Pump: Bad FPR. [Tip from Chris Daunhauer ] My fuel pump
noise (both the old one and the new one I installed) turned out to be caused
by a faulty pressure regulator up at the injector rail NOT by a bad pump.
Parts counter man insisted that from my description of the problem I had
a bad pump in the tank. He was wrong. Bad regulator was not letting excess
pressure bleed off back into the fuel tank causing external pump have to
work too hard. Thanks for the 2 suggestions, guys, they were both right.
The electric pump delivers about 10 times as much gas to the injectors
as they need. Excess is routed back to the tank. Could have been either
a clogged return to tank line or faulty regulator. In my case it was the
Here's what I learned....
If the external electric fuel pump is
noisy, pull the return line off the pressure regulator. Install a spare
length of hose on the barb and run the other end into a can on the ground.
Start the engine. Fuel should be rushing out of the hose leading into your
can, even at idle. If this excess fuel that the injectors aren't using
is NOT (mine was not) rushin out, there's a good chance your fuel pressure
regulator (about $60) is stuck closed.
Volvo mech said he's put pressure gauges
on cars w/ stuck regulators and the needle goes off the scale.
Noisy Fuel Pump: FPR Faulty.
[Tip from Jeff] I have been fighting a noisy fuel pump, rough idling, and
poor performance for the past 3 months and finally solved the problem.
It may not be a faulty fuel pump. In my case it was not. I replaced pump
and the new one was just as noisy. I checked the in-tank pump and it worked
fine. Then I disconnected the outlet or return line from fuel pressure
regulator and attached a piece of fuel line to it and stuck it in a bucket.
Nothing came out with engine running. The fuel should have been gushing
out. I replaced the regulator and I have a totally new car. It runs like
a top with no pump noise. So before ruling out pump problems check the
regulator output first it is easy and takes about 3 minutes to test.
Filter Replacement. [Query:] The time has come for the fuel filter
to be replaced. Rather than pay the dealer an arm and a leg, I'd like to
replace it myself as I have done with my 200 series. Has anyone replaced
a fuel filter on this model and year (1995 940)? Where is it located? Tips?
[Response 1: John B] It should be the
same as the 7xx cars:
Pull the fuel pump fuse while engine is
running, engine stops with no fuel pressure left in line.
[More Fuel Filter Replacement Tips]
Any tips to make fuel filter replacement easier? [Response 1: Neos]
Don't do it the way I did. I did not raise the car (740) high enough, and
doing so caused me to not have the best of angles (and room to work) to
hold all in proper position. I almost broke the line (toward the front
of the filter) that goes over to the pump. It is real easy to start it
bending to the point of having a kink if not careful. [Response 2:
Robert Abel] I've done three in the past 1 1/2 years. One was easy,and
the other two were pains in the butt because the nuts were so tight. I
actually ended up cutting one end of the filter open because the nut began
turning inside the filter. The more of the work you can do on the
bench instead of under the car, the more pleasant this task is. Remove
only what is necessary to take the pump and filter cage off, then do the
remainder on the bench. If you have an impact wrench, you will likely avoid
the problems I had. Having a fire extinguisher around is probably
not a bad idea.
Shut off engine.
Look under the driver side of the car
for a small subframe assembly, about 20cm by 15cm or so. It has the filter
and main fuel pump on it.
Drop the subframe, unplug the main fuel
pump electric connections, disconnect the fuel tank line (plug this one)
and disconnect the line to the engine.
Replace fuel filter and banjo gaskets.
Reverse to install.
[Response 3: Philip] I take somewhat
the opposite approach from Robert. During my first few changes, I removed
the filter from the bracket and then tried to disconnect the lines; it
was very difficult. Now I try to leave the filter in place as much
as possible, although I find that I do need to loosen the bolts to the
cage a little to get my wrenches in there. After the lines are off, I loosen
and push out the filter. When I put it back on, it is difficult to get
the right angle of the rubber line around the cage unless it is one of
the last things tightened.
[Another Tip:] When ever you change the
fuel filter get new copper washers from Volvo(less than a buck)!. You'll
go nuts trying to find the right size otherwise. (Editor: Wagner Brake
sells them as brake fitting copper washers, numbers F17 and F10775.
) I fought with my filter's leaking connections, replacing the fitting
between the pump and the filter which was about $25.00. All I really needed
was 2 little copper washers.. The old ones won't crush enough to make a
Deployment While Changing Fuel Filter. [Tip from Abe Crombie]
There is a Volvo SB out on precautions when changing fuel filters.
The SRS Airbag system is powered anytime the key is in position I or II.
If you are listening to radio while changing fuel filter and you are using
air impact tools there are real risks of deploying airbag as you re-install
the fuel pump/fuel filter bracket. The hammering of air impact tool on
bolts securing this bracket which is very near crash sensor location in
floor pan on inside of car, can cause a deployment. This sounds like someone
found out about this the hard and expensive way. The bulletin only
mentions 700/900 series but the 240 crash sensor is not too far away from
the same location. LEAVE KEY OFF WHEN CHANGING FUEL FILTER!! If you need
tunes get your rhythm somewhere else besides the car radio. [Comment:
S. Ringlee] By extension, then, if I use impact tools on such things as
suspension bolts or anything else likely to jolt the body while the ignition
is on, the same result may occur. $2500 lesson (bags, sensors, seat belts,
glass, speakers, heaven knows what else.) Your advice is great: listen
to a boom box and NOT the car radio while banging on the car. Thanks for
Pump and Sender Replacement. [Tips from David Schermbrucker]
Fuel sender unit:
1. My 88
745 has a plastic tank (love that Swede engineering) and the large knurled
plastic ring holding the sender unit in place. The ring comes off
easily enough with a few blows via strip of oak flooring to the knurls.
2. I cut
the rubber fuel lines since they were obviously on their last legs; these
connect the metal outpipes to the metal fuel lines that run under the car.
NOTE: Volvo uses non-standard 1/2 inch pipes; most auto parts stores
only carry up to 3/8 injector hose. Before you cut those lines have
replacements ready. This applies to the rubber lines running to the
main pump and from the fuel filter as well.
3. I got
my old sender unit (the top plate, which was rusted and the pipes cracking)
rebuilt at a local radiator shop; they cleaned off the rust and brazed
new outlet pipes into place. Much cheaper than replacing the whole
assembly including pre-pump.
4. I installed
the sender unit incorrectly (there is some obstruction in the tank that
prevented it from going in vertically; haven't figured it out yet) and
now the fuel gauge is inaccurate. Message: make marks when
removing the unit so you can align it properly. Allegedly a mark
on the top plate aligns with the plastic tank seam, but I couldn't see
4. I re-used the original rubber neck seal;
Main pump/filter assembly:
1/2 inch rubber hoses.
2. I got
a Niehoff pump which puts out 90 psi, more than needed. Price was
good and the unit came with the proper fittings for a Volvo assembly.
3. The little
aluminum and neoprene hose connecting the fuel filter to the pump was cracked
in my case; I used rubber pressure fuel line with no problem, at 1/10 the
4. I siliconed
over the electrical terminals since they face forward into the slush and
grit stream under the car.
5. All in
all, real easy to remove and replace.
[Query:] I have two 740DL Volvo's 1990.
One wagon and one sedan. Had to replace the fuel pumps on both cars.
One had 76k the other had 90k. Is this the norm? [Response:]
If your cars are both Bendix fuel system with the AC (GM parts division)
made in USA) fuel pump in tank and no pump underneath floor on bracket
next to filter, then yes it is not uncommon.
Pressure Test Tool. At last check, Volvo wanted $600 for the pressure
rig to test control, =
system, and residual pressures. I built
one for much less ... here's how. Parts needed:
2 Banjo 'nut' fittings (the ones that
actually look like a banjo). Hack apart old fuel lines from an Audi, VW,
or BMW from the wreckers to get the ones with the small nipples. Make sure
they're the same diameter as your Volvo (see the tip below for Volvo
Now, hook them up in this order:
1 Brass Tee , 3/8" NPT
1 Brass Valve, 3/8" NPT=20
1 150 psi gauge
2 2.5" 3/8" NPT brass extender (pipe w/
both ends threaded)
2 3/8" NPT brass nipples
2" vacuum hose
4 small tie wraps (zip ties)
1 nylon spacer, 2" long, that will accept
the 'bored' banjo bolts
some telfon tape for sealing
Banjo Nut - 1" vacuum hose - nipple - extender
-tee -valve -extender-nipple-1" vacuum hose - Banjo Nut
Use the tie wraps to clamp the vacuum hose
onto the banjo nuts and the nipples. Vacuum host isn't ideal for this,
but the tests are short term and a short piece of the hose holds the pressure
just fine. The gauge goes on the top of the tee. Be sure to use teflon
tape to seal all connections.
One of the banjo bolt goes where your control
pressure feed line connects to the fuel distributor. The other one gets
bolted into one end of the nylon spacer. The other end of the spacer has
the control pressure feed line bolted to it.
Now, follow your Bentley or Haynes directions
to test... when placing the tester into the fuel circuit, be sure to orient
the valve on the correct 'side' or else you'll only be able to measure
Special Volvo Fittings to Make Connection.
from Neal] Here are the Volvo part numbers for two hard to get parts needed
to build a fuel pressure gauge assembly:
9995267-7 Nipple $27.45
9995116-2 Hose $ 9.30
The nipple is the fitting that connects
between the rubber fuel line and the fuel rail. The hose includes the banjo
fitting that attaches inline with the nipple. The other end of the hose
is an unusual fitting that I imagine could connect only to a Volvo fuel
pressure gauge. I cut that fitting off, and installed a 1/8" male pipe
thread with barbed fitting pressed onto the hose. The 1/8" male pipe screws
into almost any fuel pressure gauge found at any auto store. Make sure
you get a gauge that goes to at least 100psi.
FAQ for 7xx/9xx/90 Cars
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