My previous posts on this issue are below.

Last nite, I cleaned the Idle AIr Cointrol Valve, no difference.
Installed new radio suppression relay, no difference.
Installed new aftermarket Ignition Module (Power Stage), ran very bad, faltering under power and stalling at idle.
Test drives produced no codes other than 1-1-1.
Pulled out the new IM and RS relay, and reinstalled the old parts, now it runs great?! 10 mile test drive and 12 miles suburban stop and go driving today have been flawless.

I cannot figure this one out. I think the problem is unresolved and will surface again.

Any thoughts?

Steve C

Previous posts:

"My original post from a few days ago is below. Since then I have verified the functionality of the Main fuel Pump, Tank fuel pump, mass air flow sensor, fuel pressure regulator, and throttle position sensor. Like I said in the earlier post, the fuel pressure relay was recently replaced a while before the problem started. I also attempted to find vacuum leaks using propane , but haven't come up with any yet. Inspection of the connectors for the ignition module and knock sensor were unremarkable. I retorqued the mounting bolts for the ignition module and its heat sink just to make sure.

I spent several hours Saturday reading up on the car then poking around trying to come up with a diagnosis. It seems that the car has several modes of symptoms. Sometimes, it will start and idle indefinetly, but will not take any throttle without stumbling. Somteimes the idle stays up at 1100 rpm, and the car stubles if you stab the gas pedal. Occasionally, it will barely run at all, or will not start. Occassionally, it will strat and drive normally for a few blocks, only to barely make it home running on idle because it won'ttake any throttle. The problems are independent of whether the engine is warm or cold.

I still am not sure what the diagnosis is. I am trying to figure it out before I just start throwing parts into it.

Any suggestions on how to proceed?

Steve C




"Greeting:

Today I had my 945T wagon quit a mile from home after a 5 minute warmup. Efforts to restar about 50 times produced no results. After about 15 min sitting, the car started, but alternatly sputtered, barely running, then would run fine for a bit. Engine felt as if it starving for fuel. Pulled codes, got two: one indicated that the fule pressure was either too low or too high, or that the engine was too rich; the other indicated that there was no signal from the knock sensor. The car has 126K miles, ignition tuneup and fuel filter within the last six months, and has the Bosch system, not Regina. This happened once about 8 months ago, but the problem cleared and has been running great since. How can I proceed to evaluate the problem?
Thanks.

Steve C"

I had a 91 940 Turbo (220K) acting just like this and I finally fixed it with a new coil.

Check the contacts in the relay sockets. They sometimes have been known to push back, there by giving you an intermitent contact.
--
'96 965 with 16' wheels at 120K. Had '85 745 Turbo Diesel for 200K.

Dear Steve,

Good p.m. and may this find you well. You might want to wiggle the wire to the Crank/RPM sensor, with a view to seeing if a breakdown in the wires' insulation - due to age, caused the erratic operation. This is simple to do.

Did you perchance get fuel, just before the problems arose? I recall a post - some months ago - where a flawlessly-running car, suddenly seemed possessed by demons. It turned out that a load of fuel - with water added - was the problem.

Hope you're soon rolling smoothly!

Yours faithfully,

spook

How can I determine if there is water in the gas? If the problem is intermittent, the chances of pulling a fuel line off of the injector rail and seeing water in the gas I collect in a jar is kinda' low. Is there a better way to determine whether there is water in the tank? Or do I just drop in a couple bottles of dry gas?

Thanks!

STeve C

Dear Steve,

Good p.m. Did you take on fuel, just before these problems surfaced? If not, then water-in-the-gas likely is not to blame.

If you did take on fuel, just before these problems surfaced, then contaminated fuel is a possibility. If fuel contamination is likely, I'd use only a little "dry gas". Its main ingredient is methanol (wood alcohol). Methanol attacks rubber. Thus, you don't want it in the system for any longer than is absolutely necessary.

I'd add perhaps four ounces to the gas tank. The methanol molecules will bond with any water, and allow the water to be burned. The attached water molecules do not keep the methanol from burning, when it is ignited.

Note: only add "dry gas" if you took on fuel, just before these problems erupted. If you took on fuel a week ago, the fuel would have caused problems almost at once (water sinks to the bottom of the tank).

Yours faithfully,

spook

I think I took on fuel 2-3 days before and burned through about a quarter tank. Rather than just do the dry gas technique, is there a way to inspect of test for the presence of gas in the tank?

Thanks,

Steve

Dear Steve,

Good p.m. I doubt that fuel, taken on 2-3 days before the engine began to misbehave, is the cause. If there's water in the fuel, it will sink to the bottom of the tank within minutes. The pump will send it into the fuel lines. The filter may catch some of it. However, you'll know pretty quickly that the fuel's bad, because the engine will choke on it.

The only way to examine the contents of a gas tank, is to remove the tank and to drain it. I've never done this. It is not likely to be easy.

Moreover, when a gas tank has to come out, most of the fuel has to be removed. The reasons: gasoline weighs about 6 lbs/gallon, so a full tank (19 gallons in a 940 series Volvo), weighs 114 lbs. That's a lot to handle, in addition to the weight of the tank itself. Further, the more fuel in the tank, the more has to be stored, to empty the tank. Finally, the more gasoline that has to be handled, the greater the fire risk.

If it is necessary to remove gasoline from the tank, I presume it can be pumped, using a hand-operated (non-electrically-powered) pump. Any electric device, even battery-powered, can generate sparks, that create imminent, lethal peril of fire/explosion.

Plainly, no open flames (e.g., lit cigarettes/pipes, welding torches, etc.), radiant heat sources (e.g., space heaters, toasters), or electrical motors (drills, saws, compressors, etc.) should be within 50 feet of a fuel-draining operation.

Yours faithfully,

spook

Spook:

Pulling the tank sounds pretty difficult. Of course, the safety aspects would be quite important.

I am thinking back to the days when I worked at a gas station. Periodically, the underground tanks were gauaged with a long stick to determine the fuel level. Often, the person performing this would apply some type of colorimetric paste to the end of the guaging stick. If it came back up purple, you knew there was water in the tank. The height of the color change was the height of the water.

I am wondering if there is some product or technique, colorimetric or otherwise, that could be used in this application?

Steve C

Dear Steve,

Good p.m. You've just proved the old saying to be true: one learns something new every day. I am glad to know how the presence of water - in a fixed position gas tank too big to drain - was determined.

I'd guess that a service station owner - or a company that services gasoline or oil storage tanks - might be able to tell you how they determine if water is in a gasoline storage tank. It might be the case, that a company that sells home heating oil, would be able to tell you how they test for the presence of water.

Oil is a widely-used home heating fuel in the northeast. If there's no one in your area, to whom you can ask this question, let me know. An internet search might be worthwhile.

Yours faithfully,

spook

Spook:

Thanks for the comments. I saw your note on jiggling the crank position sensor wire and tried that out last nite as well. That produced no effect and the insulation looked pretty good.

Thanks for your input, I always enjoy your posts.

Steve C

How about the Crank Position Sensor (basic ignition input signal)? You didn't state the mileage, but it's probably overdue, if original. Do some searching here and you'll find plenty of hits.

It's only about $35 and not too hard to replace (left hand, using braille).

Here is a picture of a Crank Position Sensor in place (with engine probably NOT in place).
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Bruce:

Interesting suggestion, let me ask this: If the CPS fails intemittently, would the tach needle desend as the engine winds down to stall, or would it instatly drop to zero. When the car has stalled, the tach has been tracking with the actual engine rpm. Like I told spook, flexing the CPS lead every direction produced no faults.

Thanks for the insight.

Steve C