Hello fellow car guys. I've learned a lot through the years on this forum and thought I had mastered most GM cars. I was doing well for a few years fixing all sorts of problems of my own and friends/families cars but this new beater I got is making me lose my mind.

It's a 1990 Oldsmobile Cutlas Ciera, 3.3L V6. The problem with it is that when the car is warm, it will not start. If the car is cold, it starts in a few seconds, if the car is HOT (like just shut off after driving) the car starts fine. But it will NOT start if you let it sit 10-15 minutes after you shut it off when the car was hot (fully warmed up). You must wait till the engine cools itself enough to where the coolant is somewhere around 100 degrees (or about 45 minutes after last shut down) before you have a prayer of starting it.

I've checked for spark, and spark is definately there. I've even replaced the Ignition control module, and replaced the ECM (used the same chip though). The crankshaft combination sensor was also replaced. It appears to not let the injectors fire fuel into the motor. The fuel pump definately runs, also replaced the fuel pump relay, and I even replaced the oil pressure switch. During cranking the injectors see a constant 10.75 volts or higher from each of the 2 terminals. (I'm not sure if it's supposed to be constant voltage or it's supposed to pulse?)

So when the car is fully warmed up, it's fine, and when the car is cold, it's fine, but if it's only luke-warm or cooling down, no way in hell does it start. I regard myself as pretty good in car diagnostics, but I just cannot find this gremlin. So I'm reaching out to you guys, I need a fresh outlook on this problem. This car was reliable for the 2 years that I've owned it, but just recently it has developed this problem and it's far from reliable enough to be driven everyday. Also at times, the car will shut off while driving, but that's seldom (and only started to happen after the no start problems started to occur).

Any insight would greatly be appreciated, Thanks!

P.S. There are no ECM trouble codes

 

You say you know the fuel pump runs. Is this because you can hear it? If you squirt a little starting fluid into the throttle body will the car start? This will definately let you know that it is just a fuel problem but be carful not to squirt to much when doing this as it can be dangerous. If this starts it and you haven't already then you need to hook up a fuel pressure gauge to the shrader valve when the car is having a fit. How much pressure? Sometimes the pump will run and you can hear it but this doesn't mean you have adequate fuel to start the engine. If the pressure is there but low then I would try changing the fuel filter. If this doesn't help then you need to check power and ground to the fuel pump. It needs to be at least 12 volts. Anything lower could cause the pump to run but not fast enough. Let us know what you find. Good Luck

 

I'll definately try to check out the pressure. I just need something to take the core out of the schrader.

 

This is a problem I've heard alot of people complain about, both cars and motorcycles, perhaps more old than new.

Seems in most cases I've seen, the owner of the vehicle in question will try to start the vehicle, ( after the 15-20 min cooldown) without giving it any throttle. When pushed for an answer of why they do this, most people say "because if I give it throttle, I will flood it".

My personal experience on this behavior, which alot of my cars and motorcycles have indeed had to greater or lesser extent, is that it's quite the opposite which is the problem; it's because you DO NOT throttle it it won't start.

In most owners manuals, it states clearly that you should give it some throttle while starting the engine if after a cooldown period such as this. My old Harley with a kick start had this aswell, and kickstarting it is something you want to do as little as possible, so what I found out was, if I gave it full throttle, it started alot easier. And I did it that way when lukewarm, not having any more starting problems for the 12 years I owned it.

Although I tried to tell alot of people this, especially the ones kicking an old panhead to death on sunday afternoon after camping on a rally, most wouldn't lissen, and went on with "oh no, I might flood it"

I also start my thirdgen this way, and a fair number of other cars I've owned, some also fuel injected.

Now being that this car is fuel injected, it might not be as easy as this. But the point is, the car needs extra fuel when starting lukewarm (or maybe it's extra air, I'm not really sure). I don't know all the ins and outs on your cars fuel injection system, so I can't say that it has a circuit for this, or something in the computer or not. If it does, it might be the enrichment circuit or extra injector not working properly, but then again, it might not have this system at all. My first thing to try would be to try starting it with the gas pedal half way in, or full. If that don't work, I would read up on how the injection system is built, and see if there is in fact an enrichment circuit, and then try to trouble shoot it.

In worst case, the enrichment might be in the ecm using the main injectors, in that case there might be a temp sensor showing a too low reading, so as it won't engage the startup enrichment soon enought. You might be able to "trick" the computer with a switch grounding the temp sensor, but it should be fixable to a stock and working state.

My mother had a brand new car which was like this, on the commute to work at about 5 minutes driving time, there used to be some slowgoing traffic where the car always stalled. She then tried starting it again and it took forever. Me being a car enthusiast at early age, tried to lissen to my moms problems and really wanted to help her, but I remember clearly that she said the garage/ dealer had told her to NOT give it any gas as not to flood it. They never where able to fix the car no matter how many times thay had it in the dealers garage, so my parents rather just bought another new car and sold it.

Years later I found out that a friend of mine had in fact bought that excact car, and when I asked him if he had starting problems with it, he said "yes, initially, but I learned that I had to give it throttle, and after that it wasn't a problem anymore".

Alot of talk there, hope you see my point, don't bother searching for ignition problems or fuel filter/pump problems as thats not very likely if it runs fine at all other times. Good luck.

 

With the proper fuel gauge attachment you don't need to remove the core, however if you are just going to clamp a hose over it then all you need is a standard core remover for tires or ac or anything.

 

Tilstad - Thank you for your insight. I have tried starting the car with throttle (to give the engine more air) but since it's fuel injected, I'm at the mercy of the ECM as to how much fuel is being pumped in, I can pump the gas pedal all day long but all I'm doing is letting air into the manifold, nothing more. I used to own an '86 LG4 bonneville, and I was quite aware of the fact that I had to give it gas to start it. But with this '90 Olds I just have no idea. I've swapped LT1s into 2 different thirdgens without so much as a start-up problem, and I've resurrected a TPI Thirdgen that an owner left for dead. I thought I had a well based knowledge of GM vehicles, but this '90 just leaves me scratching my head. With no trouble codes from the ECM, I feel like a blind man walking through a forest. I'm at the mercy of replacing nickel and dime parts till I hopefully stumble onto the correct problem. The parts store gives me the stink eye with every part I return and claim I have not installed (I try to clean it up best as possible lol) but this has gone on for a better part of a month and this car has left me stranded for a good amount of hours now.

One more piece of insight I may have forgot to mention. Sometimes the car will start up, and run for 10-15 seconds, and then just shut off like if someone turned the key. It's not a VATS system since this car does not use it. I could be in the middle of a rev, or even starting to drive the car and it'll just die like someone turned the key to turn it off. A few hiccups like this and eventually the car will just keep running and I'll be OK to drive it, but it's incredibly annoying and just not safe.

I'll try to check fuel pressure, but I just don't feel like the fuel pump has anything to do with it. How could there not be a problem 95% of the time, but only during starting when the engine is luke-warm will there be a problem? Seems like the ECM is seeing something (or not seeing something) and cuts off fuel. I'm just at a loss.

 

Well, I've only had one injected car with intermittent problems, like stopping for no reason, and won't start again until 5 minutes or even hours or days have past. The most frustrating thing about that, was that for the most part the car worked. So when I had time to troubleshoot the car, it was impossible to find any fault with it since it worked, at that time.

The final solution to it was to go to the junkjard, find the exact same model and engine, and pull off every single electrical part of the injection system. I then put everything into the airbox since I also needed that because of the attached AFM, and then put everything on their desk and asked "how much for this?" $15.

So what happened after that was I simply drove the car until it stopped, and tried to swap some parts. First time around the car come to it's senses before I found the fault. Second time, I had of course left the rest of the parts at home since I figured I fixed it the first time, and had to get a tow.

But the day after I want through the rest and found a simple module to be the sinner. It was a control module for a the idle stabiliser system.

Hard to guess or find faults when it's intermittent. I'd search ALL OVER the place for corrosion of contacts and grounds first though if I where you, like I did myself. Hope this helps.

 

Well I just checked te fuel pressure, and it holds steady at 35 PSI with the vacuum unplugged off the Fuel Pressure Regulator. With the vacuum hooked up, it holds at about 22 PSI at idle and steadily increases with throttle. No matter what the temp of the motor or even during cranking, I get a constant 35 PSI at the FPR. According to a Haynes manual I'm supposed to have between 28-36 PSI at the FPR, so it looks like the fuel system is OK. I just don't know anymore.

 

I know you're just going to think this is a "brain-dead" idea but have you checked the spark plug gap? Most people pull a plug and "it looks fine", never checking the gap. Another thing to try is the MAP sensor (if equipped) and O2 sensor. Just my

 

You could have a bad coolant temp sensor which would account for an open loop start and trouble starting once the car is warm and goes into closed loop. However, this is not 3rd gen related. Sorry.