1990 740 GL Stalling/Starting Problems

kgneff · Post by **kgneff** » 18 Aug 2007, 11:06

Hello all,
My situation is this: My parents made me a deal, if I get the volvo running, it's mine. The car had 225,000 miles on it when the odometer stopped working (one of those little things I have to fix

). It had been sitting in the driveway for 3-4 years, unable to start. The car turned over just fine, and it had spark from the spark plugs, plus it would rev up on starter fluid, so the airflow was working fine. I was able to diagnose the problem to something with the fuel system. After replacing the Injectors (which appeared to be clogged), Fuel Pump (was seized up/blown), Fuel Filter (might have been original to the car), and the Fuel Pump Relay (one of the connectors had burn marks), the car magically started right up.

The car ran perfectly for a month, and I went about fixing the little problems (a blown speaker here, a dangling overhead light there). Then it began intermittently stalling when I'd come to a stop at a traffic light. But it would start right back up, no problem. Occasionally, the car would start to stall out, but rev it self back up (as if I had tapped the gas).

At about the two month mark, the car stalled out while I was waiting to pull out of a parking lot and wouldn't start back up. One tow truck ride later...

I tried my key in the ignition and it fired up just fine. I took the car out again, and the same thing happened a second time, this time the car wouldn't start on it's own even after getting it home.

I did my basic diagnostic again. It had spark, it had airflow, it had fuel pressure to the injector rack (so it wasn't a pump problem). I took the injector rack off the engine and reconnected the electrical, no fuel came out of the injectors while I tried to start the car. I took a multimeter to the injectors' electrical plugs, all of them show current when the key is in the on position.

However, while showing my dad the problem today, the car started up on starter fluid and then continued running on it's own power. I turned it off and tried restarting it and it fired right up, this time on it's own. So, now I have a running car that I don't trust any farther than I can push it.

I really don't know what I should do next. I like the car (and the low insurance rates it gets a college student like myself). I would love to take care of the problem myself, so any advice is greatly appreciated (even if it is that I just need to take it to a qualified mechanic).

Thanks in advance,
Kyle Neff

Kmaniac in California USA · Post by **Kmaniac in California USA** » 19 Aug 2007, 07:18

I got two questions for you:

Which fuel pump did you replace (size and location)?
Which fuel filter did you replace (description and location)?

My 1986 740 has TWO fuel pumps and TWO fuel filters. I believe this design was carried through into 1990, but I'm not that sure. Check your fuse box for a fuse labeled "in-tank fuel pump" to be sure.

If you have a single pump system, your fuel pump should be quite large and in the tank only.

If your fuel system is like mine, you will have a small fuel pump in the tank called the "in-tank" pump. It is mounted on the fuel pick up and sender unit assembly. On the pick up end of the pump is a filter sock. This is the first of two pumps and filters. Then, under the car, below the driver's seat, is the main fuel pump and the main fuel filter. Both are large cylinders. These will be the second of the two fuel pumps and filters.

If you have a two fuel pump system and replaced the fuel pump and filter under the driver's seat, but did not touch or look at the fuel pump and filter in the tank, you will suffer the problems you have right now.

The problem with the two pump system is that most Volvo trained mechanics don't regularly service the in-tank pump and filter. But over time, the filter sock in the tank deteriorates, causing dirt to enter the pumps. The first pump to go is the in-tank pump, but most people don't know this because the car will run on just the main pump. The only possible indicater of an in-tank fuel pump failure is a blown fuse for the in-tank fuel pump. But sometimes people see the blown fuse and replace it, not knowing what it means and not solving any problem. Mechanics unfamiliar with Volvo's design don't even realize there is a pump in the tank. Over time, more dirt enters the main fuel pump and slowly starts to deteriorate that pump, too. The main pump will slowly start to work intermitantly until it finally gives up. But most people get so frustrated with the intermitant starting that they either sell or junk the car first.

Sounds to me like your car has the two pump design and both pumps got jammed with dirt from a bad in-tank filter sock. This lead to the car sitting for four years. Then, you cheerfully replaced the fuel pump and filter under the car (not knowing there was one more pump and filter in the tank) and got the car running. But, after a while of sucking dirting fuel through the new, replacement pump, this pump is starting to deteriorate, causing you these intermitant starting and stalling problems.

In the short term, carry a small rock with you, one that fits in your hand. the next time the car stalls and won't start, tap on the fuel pump under the driver's seat a few times and try to start the car again. If it starts after the taps, you need a new main fuel pump. Never replace a main pump without also replacing the in-tank pump at the same time.

Check your fuse box for the in-tank fuel pump fuse. If you find it and its blown, time to replace both pumps and in-tank filter sock together.

Now, search this forum for my past posts on fuel pumps for more detailed information. Read and think about what I have said. Let me know the answers to my questions and whether any of what I said rings true for you.

kgneff · Post by **kgneff** » 19 Aug 2007, 08:29

Thanks for the response, but sorry, I probably should have specified this car is a one pump car (in tank). I'm certain of this because I also replaced a good deal of the fuel line. I replaced both the in tank sock and the filter under the driver's seat, those were the only filter's in the line. So, I guess that's not the problem.

I was a good little newbie and did a search before I posted, to no avail.

Thanks again for the response, I truly appreciate it.

Any other ideas out there?

kgneff · Post by **kgneff** » 18 Sep 2007, 22:52

Update and narrower problem!
Please note, I've included all of these details in the hopes of lessening the back and forths of problem diagnosis, the actual question can be found by skipping down to the last paragraph. As always, thanks in advance for any and all responses.

I took the car to my mechanic and, after much delaying, he diagnosed it as a faulty Idle Air Control Valve. Which he promptly priced at $400.

I decided that the part was simple enough for me to attempt the replacement myself. I drove the sputtering car the 10 blocks home and on the last block it stalled out and wouldn't restart...again!

Picked up the part for $100 used from a local parts shop. Popped the part in, and....nothing. The car still won't start.

So, back to the drawing board. It still fires up nicely on the starter fluid (but never runs on its own). However, when I disconnect the fuel feed line from the injector rack(with car off, of course), there's no residual pressure (fairly certain there used to be before this fiasco). I think this may be the source of the problem; or, at least a primary symptom.

When I remove the injector rack from the engine and turn the car over, nothing comes out of the injectors (pretty sure that used to happen too). I know there is good fuel flow from the pump, it just seems to be running right through the rack. My first thought was the fuel regulator. I happened to have a spare, used one lying around, so I swapped that out. No dice.

So, after that long explanation of symptoms, the question boils down to this: What could cause there to be no residual pressure in the fuel line/injector rack? Could that cause my injectors to not be releasing any fuel, therefore not starting the car?

A hopeful thanks again,
Kyle Neff

wojeepster · Post by **wojeepster** » 20 Sep 2007, 15:18

I vote for a bad fuel pump relay. When car fails to start flick the fuel pump relay with your thumb and forfinger. If car now starts replace relay. $20 at fpcgroton.com, I paid $47 at the dealer.....

kgneff · Post by **kgneff** » 25 Sep 2007, 17:41

Sure enough! That was it. There was a severe amount of corrosion around the connectors for the Fuel Pump Relay, so I cleaned them up and it runs good as new!

$200 later, and it turns out to be a free fix. Well, I cannot thank you enough. What can I say.

Thanks again,
Kyle Neff

wojeepster · Post by **wojeepster** » 26 Sep 2007, 19:45

Glad you got it. It took me two weeks with my wife's 740 but I was new to fuel injection then. I diagnosed my 240 with the same problem in 5 min! It is common to volvos so I carry a spare fuel pump relay....I have not needed it though after the first replacement. I also carry a spare air mass sensor (horribly expensive at dealer but available cheap on

www.car-part.com I bought two good ones for $20 each.

If you are going to be looking at any more electrical stuff I recommend Tracy Martins "How to diagnose and repair automotive electrical systems" about $17 on amazon.