Bill --

A defective engine temp sensor (the one near cylinder #3, not #2) or a bad connector, connection, or wiring can "fool" the ecu into thinking the engine is at about minus 40 degrees, which is pretty damned cold (regardless if it's F or C).

The ecu will respond by dumping in tons of fuel. If it doesn't ignite, this fuel will wash down the cylinder walls into the oil.

Loss of oil on the walls means loss of compression. You can correct this by squirting a teaspoon or two of clean motor oil into each cylinder. (When it fires, expect smoke for 5-10 minutes.)

A symptom of this is an engine that cranks fast, and has a tendency to "wanna start." That is, a few pops, farts, grunts, etc.

Also, if you've had this problem, change the oil at the earliest convenience. It's diluted with gas, which means it won't lubricate well, and it also poses an explosion risk.

Don Foster (near Cape Cod, MA) --
Re: No Start - Ignition Control Unit - A Lesson in Physics and Chemistry[700/1989] posted by Bill Peyton on
Monday, 1 January 2001, at 10:23 p.m.

Hi Don, Steve, Bob, Brian, John -

First off a very big THANK YOU all for your advice and suggestions. This was a completely baffling problem, because everything that was supposed to be working was working - except for the car.

Cutting to the chase: The first problem was a shot Fuel Pressure Regulator, with gas on the vacuum side. In the course of wailing away on the thing, it dumped about two quarts of gas into the oil. With no viscosity, and a high mileage engine, I did not have enough compression to fire the mixture.

Don's suggestion above was dead on, in terms of getting the car started. A little clean oil in the cylinders, wire brush the plugs, and viola - a car that runs, with an automatic smore screen generator.

Then I changed the oil and the filter - disgusting. Warm, it was about thin as water, and smelled foul.

Since then, it ran beautifully except for one thing: Afer a 20 minute drive, once I put it into Park, it began to hunt from 1000 RPM to 1500 RPM. I'll see how it behaves over the next few days and keep my fingers crossed.

To keep others from this pain and suffering, here is a summary:

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A) Early warning sign: The car would hunt and stall when you put it into Park or Neutral. (The fuel pressure regulator was over pressurizing the car, the computer could not adjust fast enough.) The car would stall when coming to a stop, or if you accelerated too quickly from a stop.

At that time, I discovered the in tank pump was not working and replaced it, and the main fuel pump, which was working OK, but I figured, it has been laboring without the in tank pump, let's just do all this at once. BTW, the Bosch part is about $125 cheaper than the Volvl part with the same number. This helped for a while, then...

B) Car failed to ignite one cold morning last week. Cranked, but did not fire.

C) Pulled plugs from the #1, #2, #3 cylinders. Gas poured out of #2 on cranking, nothing significant from the other cylinders. But no ignition. Plugs soaked with gas, but showed a weak spark when grounded.

***********************************

Checked:

1a) Fuel Presure Regulator: Gas on the vacuum side. Replaced early in the adventure, but the gas in the oil did me in.

1) Engine coolant sensor. Pulled, tested resistance cold and hot, hotter it gets, the lower the resistance. Tested both leads to ground, they were positive.

2) Knock sensor: Tested leads to ground, one connected, the other did not. Seems to be normal.

3) Idle Air Control Valve. Vibrated when the ignition came on, visual inspection with hoses off showed something happening in there. Cleaned, put back in place.

4) Ignition: Replaced coil. Now got a very healthy spark from #1, did not check the others. The cap, rotor, wires, plugs have about 10K on them. Fuel filter has about 10K too.

5) Injectors: Pulled all four plugs after the FPR was replaced, got a nice fine mist from all four cylinders. (Disconnect the high tension lead from the coil to the cap, PLEASE.) TO me, this also ruled out the Hall Sensor.

6) Fuel Injection Pump Relay. Found it first with Jim's help. Main fuel pump comes on when the car is cranking. When jumpered from 30 to 87/2, both pumps ran. This also ruled out the Overpressure switch.

7) Timing: Pulled top cover, inspected belt. Cannot check all the marks without additional surgery. Belt is new (10K miles) had no cracks or missing teeth. So I concluded that it had probably not slipped a notch.

8) Air Mass Meter: Identical (i.e. non starting) behavior with it plugged in, or plugged out.

9) Fuel pressure: I never got the gauge and the fittings. I will. Recommended if you are going to work on cars with any EFI system.

***************

After the car started up: Sprayed carb cleaner all around, the idle speed did not increase (No vacuum leaks)

***************

Anyway, you can see why this was such a difficult problem. The answer is only obvious in hindsight, and everything seemed to be working the way it should.

So thanks once more - the BB is a great resource!

Bill