This past week suddenly I have this problem:

As normal, I turn the ignition on without pressing on the accelerator. Starts but then immediately dies. Only when I restart then hold down the accelerator at a somewhat high rpm for at least 2-4 minutes, then the car will idle fine.

Subsequent starting works fine, until the car sits for several hours. Then same problem. BTW- it's pretty warm here in central PA this week :-)

I've had an intermittent problem with the car stalling (in the past) while sitting at a traffic light. I haven't driven the car at all this week for fear it will die on me in traffic.

Because I happened to have a new gas filter on hand, I decided to install it yesterday. Hasn't seemed to have had any impact on the problem.

As per Bentley, I measured the voltage at battery terminals (while running) = 14.64 volts. Voltage at the main fuel pump terminals is 13.46.

I then measured the output of gas from the fuel pressure regulator (return), using the procedure in Bentley for running the pumps without starting the engine (page 230-2). I got 20 ounces (600ml) in exactly 30 seconds.

I can hear and confirm that both main fuel pump and transfer pump are working (With my poor hearing I need to take the gas cap off and stick my ear right on it to hear the transfer pump).

Two months ago I did a bunch of maintenance on the breather side of things- new flametrap, new oil separator, cleaned TB, new breather hose, new intake mainfold gasket, etc.

No unusual noises or smells. The only other thing I can think of that might be relevant- when replacing the old fuel filter I got some pretty dirty gas flowing out it. However, the gas I got from the return (off the fuel pressure regulator) was clean (this was after fuel filter replacement).

I don't own a tach or pressure gauges/related.

Don't know what to try next. If I need to inspect the transfer pump, what parts should I have on hand prior? What to use as a replacement gasket/adhesive under the access plate? I've been looking at the FAQ, but unsure how appropriate those details are to my 1991 240- seems much more complicated than Bentley suggests.

Could this be a fuel pressure regulator or the fuel pump check valve?

Thanks,
Keith Ostertag
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1991 240 Sedan B230F LH3.1 M47 300K miles

There's a small device under your intake manifold called the IAC or Idle Air Control. It's an electrically activated valve that regulates air flow through the idle air circuit, and it's notorious for getting dirty (especially if you've neglected your Flame Trap maintenance (or else don't use synthetic oil, which tends to keep the Flame Trap clean).

Read the FAQ's on diagnosing and cleaning the unit.

Hi Keith,

Pull the hose on the front of the fuel pressure regulator and sniff to see if it has a strong gas smell.

Travis

Hi Travis-

OK. Hmmm... I wonder what you are implying? It smells faintly of gas... isn't that expected? You are talking about the vacuum hose, right? Can you elaborate? Are you suggesting that the vacuum hose should not smell like gas, and that if it does that suggests the regulator needs replacing?

I'm going to check the in-tank sock in the next few days after the parts arrive...

Thanks,
Keith
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1991 240 Sedan B230F LH3.1 M47 300K miles

Pull the vacuum hose from the front of the regulator, if it has a strong gas smell it could mean the diaphragm in the regulator has a hole in it and then the regulator would need replaced.

Travis

Hey Thanks Travis. I don't think the very faint gas smell from the vacuum hose is enough to indicate a problem with the pressure regulator. Next month I may get a chance to have an experienced mechanic friend check the fuel pressure.

I replaced the "sock" on the in-tank fuel pump today. Didn't go too badly- spent a few moments wondering how to get it out, but eventually it came out easily. The old one didn't really look that bad, and in fact I decided not to replace that small in-tank hose since it looks like new. We'll see in the next few weeks if the new sock helps. I'll also wait awhile to test the fuel rate/flow again.

After replacing the broken air hose the car is running OK.

Keith
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1991 240 Sedan B230F LH3.1 M47 300K miles

Which broken air hose are you talking about?

Phil

Hi Phil-

The Air Intake Hose (AKA accordian hose) evidently had a hairline crack where the connector from the Air Breather Hose (from the IAC) connected. Finally it completed sheared off, see the photo posted in the thread. That was causing the hard starting, evidently, while it was just a hairline crack. Now that I have replaced the accordian hose the car starts fine. Runs OK. But I still want to get to the bottom of the fuel rate/flow problem- I measured only half what it should be. I'm gonna see if a mechanic friend of mine can measure the fuel pressure in a few weeks.

Thanks,
keith
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1991 240 Sedan B230F LH3.1 M47 300K miles

If the FPR is leaking, gas will show up in the vacuum hose.

If I were you, I would buy or borrow a fuel pressure tester gauge, they are fairly inexpensive, especially relative to the parts you playing with.
With a gauge you can quickly see if your start problem is due to no or low fuel pressure, and whether the FPR is working correctly. Saves lots of guessing and random parts replacement.
If the fuel delivery was low, I had that on my 84 Turbo. Although the intake pump was running, and drawing the correct current, it was not pumping enough fuel.
However low fuel supply, I would not think, would effect idle, there is plenty of fuel for that, it shows itself at full throttle, when the demand for fuel flow is high.
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245 Classic M47, 245SE AW IPD bars, 84 1/2 242 Tic IPDbars & Springs, 89 745 16v M46, IPD bars, 89 744 16v M46 IPDbars

Didn't notice you touched the Idle control valve. I would pull it, and spray some throttle body cleaner in it. Hold it openings down, spray and spin it back and forth to work the cleaner through the flap/door.
Last tune up?
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Post Back. That's whats makes this forum work.

Hi Walt-

Do you mean the Air Control Valve (below the TB)? Yea, cleaned it when I did the TB and other breather related stuff two months ago. Also, I replaced the plugs and plug wires.

Thanks,
Keith
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1991 240 Sedan B230F LH3.1 M47 300K miles

Cap and Rotor along with those wires?
When it stalls at a light. does it slowly idle down or is it a quick shut down?
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

Hi Tony-

No, I have never changed the cap or rotor. It's been awhile since it died at a light... at that time, it would die fairly slowly, maybe a few seconds? As though it ran out of gas, a gradual slowing of idle.

Doesn't the fact that I only got a half-liter of gas out of the return in 30sec point to a pump related issue? Bentley says I should have gotten a little more than a liter.

Thanks,
Keith
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1991 240 Sedan B230F LH3.1 M47 300K miles

Sorry Keith I cannot add any advice about the fuel.. I never had to do that kind of diagnostics. But yeah if that's what Bentley says... sure sounds like a problem.

Did you say you checked the front hose on the fuel pressure regulator for gas in the hose?


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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

Hi Tony-

I disconnected the hose that is attached to the rear of the fuel pressure regulator, which AFAIK is the fuel return, and connected a hose from there into a container. In 30 sec I only got 600ml, I should have gotten over 1000ml.

BUT- New Development! I tried starting the car awhile ago and it wouldn't run worth crap. I opened the hood and found one of the hoses that attach to the breather hose had sheared off the breather hose body! FCPGroton says they will replace it under warranty. So maybe there was a hairline crack in it that was causing the problem.

BUT I still want to diagnose/fix the fuel flow problem, which is unrelated.



Thanks for your help!

Keith Ostertag
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1991 240 Sedan B230F LH3.1 M47 300K miles

I don't know why photos don't always show up...

Here's another try:


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1991 240 Sedan B230F LH3.1 M47 300K miles

I have found that any air leak behind the AMM will cause an intermittent stall or run rough and then stop doing it for a while.

I would say, just as intermittent as the crack opens. IMHO, that broke hose sounds wonderful for it. Lean running fits this scenario. This will add to the possible overnight shut down symptoms.

As far as the hard starting after a being, off. The fuel pressure regulator has a slight edge of failure rate over the fuel pumps check valve due to the materials used in its design.

Both will cause loss of fuel line staying filled at zero rest pressure. A leaky injector is at the bottom of a most lists without a running rich problem.

I would rule out the regulator first as it easier to inspect or as far as that goes, replace it for diagnosis.

Dirt can hit the main pump check valve if the sock strainer in the tank is bad. It can cause a leak down because trash can lodge within the spring or hang under the check balls seating surface. If the spring wears out inside, it will be hard to start, almost, all the time depending on the age of the main pump. I found that out on my oldest car.

Any dirty fuel outflow from that main fuel filter is something odd. I have never seen that before. I would think the dirt would have stayed caught within the filters pores. That filter may have started to dissolve for being on there too long. For Bosch that would have to be for many years!
Was it a Bosch or aftermarket unit? Keep that in mind if you have to consider the tank sock and check valve.

I will hold out for an air leakage as fuel smell worse, even from here. (:)
Phil

Hi Phil-

Thanks. Yea, what a surprise to find that breather hose broken! Does seem to explain the starting problems. But the low fuel pressure/flow is worrisome. Since the regulator is $$$ I will start with the easier/less expensive checks- as you say, the sock and the check valve. Parts should arrive tomorrow or so, then I will start looking closer...

Keith
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1991 240 Sedan B230F LH3.1 M47 300K miles