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.

 

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).

 

Here's an idea for you. It sounds like you don't know whether you have a
fuel problem or a spark problem. Carry a can of spray carb cleaner with
you. Whwn the car does it's thing, spray for a few seconds into the air
intake hose. If spark is present the car should start for a moment, then
die. This at least tells you if you have a fuel problem or not, then you
know which way to go to correct your situation.
Your symptoms are exactly that of an electronic module on it's way
out, like a pickup sensor for example.
Good luck, Richard.

 

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.

--
Mike F.
Thornhill (near Toronto), Ont.

NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

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.

Cheers,
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.