cold start problems
Thread Starter
6th Gear
Joined: Jul 2009
Posts: 6
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From: Duluth MN
cold start problems
My 91 L98 just developed a cold starting problem. We just got back the other night from a 1000 mi road trip for its first long drive after a long winter in storage, the car ran great. I went to start it the next morning and it took a lot of cranking before it would start, would fire and then die, finally took and seemed to run lean for a couple of minutes. I warmed it up and took it out on the road and it ran fine. So today I tried to start it and same thing, did some investigating and noticed that when the fuel pump was priming for its 2 seconds and before actually cranking the motor I heard a slight hissing noise, possibly air? no obvious gas leaks, coming from the plenum area. Another probably not related syptom is the check guages light is coming on intermitently, guages all read normal. I'm going to pick up a fuel pressure guage and do some more diagnoses as soon as I get a chance, I'm wondering if anyone has any ideas on what to look for or any common issues that might cause this.
Thread Starter
6th Gear
Joined: Jul 2009
Posts: 6
Likes: 0
From: Duluth MN
The motors got about 4000 mi on a complete rebuild, the work was done by a very reputable rebuilder. I don't think its a compression problem. Tried different throttle positions and even held the pedal to the floor in case it was flooding. It starts just like my old Yamaha motorcycle does if its cold out, won't fire if I give it any bit of throttle and just have to go through the crank and fire cycle for a while till it finally keeps running. With the bike it's a common yamaha lean thing. I just went out and had my wife turn the key on while I stuck my ear near the noise, its kind of a gurgling sound from near the fuel pressure regulator, possibly thats the problem? never heard a noise like that before. just bought a fuel pressure tester, will check that next
Thread Starter
6th Gear
Joined: Jul 2009
Posts: 6
Likes: 0
From: Duluth MN
The reading was 40 psi, manual says it should be 48-55, low enough to cause the starting problem? No visible gas when I pulled vac line, smelled gas inside line but I would think thats normal.
Thread Starter
6th Gear
Joined: Jul 2009
Posts: 6
Likes: 0
From: Duluth MN
Just read your post again retiredsfc97, I don't allways read all the instructions either. noticed you said if the line has a gas smell the fpr is probably bad, sounds like a likely cause.
Thread Starter
6th Gear
Joined: Jul 2009
Posts: 6
Likes: 0
From: Duluth MN
The problem turned out to be the coolant temp sensor. I replaced the fpr and no luck. I managed to get it started and noticed the radiator fan would start running shortly right after it started with the engine cold so I replaced the sensor. Was reading a warm engine so the richer fuel mixture for a cold start was'nt there. It started right up this morning. From what I've heard these sensors are a pretty common problem.
