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DESPARATE! 1989 760 turbo hot start problem

I posted some months ago about a hot start problem with my 1989 760 turbo (190,000 miles with a new head and head gasket). In short, when the car gets warmed up (normal driving or sitting in the sun all day) it *sometimes* will require extensive cranking, up to 20 minutes or more, before it will start. This happens even on the coldest of days in the winter. Usually, just having the hood open for 5 minutes will remedy the situation.

To date, I've done everything suggested on Brickboard, and some other things not explicitly recommended. Here's what I've replaced: Hall effects unit, power stage module, fuel injection relay, ignition coil, radio suppression relay. I cannot tell from the Brickboard descriptions whether my car has a flywheel position sensor or not (it *does* have the Hall effects, so I concluded there's no flywheel position sensor).

The car is at a local mechanic's facility right now, but they cannot reproduce the problem; naturally, since the car refused to start for me two days this week after being parked in full, bright sun all day.

I'm running out of ideas, and out of patience with this car. I'd appreciate any suggestions at all.

Thanks,

--Dale

P.S. If anyone's interest in buying this car, it may be on the market very soon if I can't solve this starting problem.

Reply to
Dale James
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Fuel injectors?

Maybe you are having trouble with fuel pressure or lack of.... or vapor lock. You need a fuel line pressure test, to see if the injectors are leaking down, or if the fuel pressure regulator is even working.

Typically a Hall sensor is like a flywheel position sensor, a hall effect trigger is a magnetic switch (creates the Hall effect, produces a small amount of voltage when the magnet passes the sensor). Does your setup use a distributor? If so, the hall effect sensor does something different (I'm not familiar with your year).

But like I said, it sounds like your injectors may be at fault, leaking down, and creating a vapor lock condition, thus the hard start, and believe me, IT WON'T!! no matter how hard you try.

This requires special equipment to measure pressure bleed off while hot (it measures if any fuel is seeping past the injectors, or they can be removed and tested on a bench under pressure).

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Reply to
Davis Redding

Reply to
R Weinberger

Except the fact that the tach is jumping when the car is not starting (noted in other thread) means that the secondary side of the ignition is working. So you can rule out the hall sender and igntion power stage. What you can't rule out is the coil, or anything in the fuel system. However, there's a fairly long list of new parts in this case which does rule out the coil, and some of the fuel system.

So the next step will be travelling with tools. In this case I'd look at the electrical connections to the fuel pump to make sure they're clean and tight. The next time that the problem happens, touch the fuel pump as the engine cranks, to see if it's running. Having a temporary test bulb connected to the wires going to the pump will tell you if it's getting voltage. If the pump is running, then opening up the fuel return line up at the rear of the fuel rail will tell you if fuel is getting up to the engine. Have a couple of rags to catch any spilled fuel. Of course for some of these tests you'll need a helper to crank the engine.

Reply to
Mike F

Hi, I had the same problem with my 1974 FI 144. I know it is many years apart from your model. My problem was a perforated diaphragm on the fuel accumulator. The resting pressure in the system would "just comply with specs". After living with the problem for about 3 years I took the accumulator off, drained it then shook it and there was still gas in it - this was a give-away to diagnosing the fuel was trapped behind the diaphragm. Perhaps your 1989 model has a fuel accumulator. The Volvo parts department told me the accumulators never need replacing. I ignored them and bought one and I have not had the problem since. I used to manually lift the air sensor plate with the switch disconnected to prime the fuel system with gas - that was my work around for three years. Your system may be a lot different than mine. But if my story leads you to a solution then it was worth while me posting my story.

Reply to
Blink

This is just a guess but mt '92 850 sometimes fails to start at the first attempt, from then on it will only start if I continue to turn the engine over at least 30 times until it finally catches. I am told that these engines have hydraulic tappets and that if oil gets under the tappets the valves do not close so you do not get compression. To start my car I always make sure that it has fired and running before I let the ignition return to normal.

Reply to
ramjet

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