Hard start when hot

[RonJ]

My 85 L98 starts really well when cold or when warmed up after driving around town. It idles well, gives good gas mileage on the highway or town, but it doesn't want to start when it's real hot.

If I have running on the highway for any length of time, cruising around 65-70 mph and then pull into a gas station for instance, in the length of time it takes to fill the tank etc., when I go to start it, it will have to crank for 30 seconds or more before it fires up if it doesn't catch in the first few cranks. It cranks over really well and sometimes when it finally catches, it almost sounds like it's loaded up. I've tried leaving the gas pedal alone, I've tried holding the pedal half down or right to the mat when I see it isn't going to start. Gas pedal position doesn't seem to make a difference. Once it starts, it runs nice and clean and works the way it should.

Anybody offer any suggestions or point me in the right direction on this one?

Thanks .... Ron ...

 

[vetteboy86]

Could it be a timing problem:confused

Craig

 

[Edmond]

It's possible that the starter and/or it's connections have gone bad. You can have an auto shop check the starter to see how strong it is. I believe Pep Boys does it, at least the one here does it, for free of charge.

If it is the starter, it's a very easy fix. The most difficult thing will be getting enough room to work underneath the vehicle because of the low clearance. There are only two bolts holding the starter on. They generally run in the $160 neighborhood. The starter is located on the passenger side not too far away from the exhaust manifold. I would suggest letting the vehicle cool down because exhaust manifold burns really hurt!

And if it is the starter and you decide to change it out; make sure to get a set of shims just in case. You don't want to have to run back out to the auto store, waste the time and gas money to get a $2.00 set of shims.

 

[iron cross]

My 85 L98 starts really well when cold or when warmed up after driving around town. It idles well, gives good gas mileage on the highway or town, but it doesn't want to start when it's real hot.

If I have running on the highway for any length of time, cruising around 65-70 mph and then pull into a gas station for instance, in the length of time it takes to fill the tank etc., when I go to start it, it will have to crank for 30 seconds or more before it fires up if it doesn't catch in the first few cranks. It cranks over really well and sometimes when it finally catches, it almost sounds like it's loaded up. I've tried leaving the gas pedal alone, I've tried holding the pedal half down or right to the mat when I see it isn't going to start. Gas pedal position doesn't seem to make a difference. Once it starts, it runs nice and clean and works the way it should.

Anybody offer any suggestions or point me in the right direction on this one?

Thanks .... Ron ...

Well for sure it`s not the cranking or charging system [starter or alternator]. Holding the gas pedal anywhere will also not make any difference, it`s fuel injected. Try a fresh set of plugs.

 

[ocrick]

Check the fuel pump relay....sounds like you are powering the fuel pump from the oil pressure switch. If you want to check....hook a fuel pressure gage onto the test port and tape it to the windshield for a while. When you turn the key you should also hear the pump pressurize the line for @ 2sec. Good luck!

 

[RonJ]

Check the fuel pump relay....sounds like you are powering the fuel pump from the oil pressure switch. If you want to check....hook a fuel pressure gage onto the test port and tape it to the windshield for a while. When you turn the key you should also hear the pump pressurize the line for @ 2sec. Good luck!

Ocrick, I think you may have nailed it. I didn't suspect the relay because I could hear it working when I start the engine cold. When it's hot, with the fan running, (it comes on early), I couldn't hear it but assumed it was OK. I got a gauge on the rail to-day, guess what, pump wasn't coming on when the ignition was turned to the "ON" position but would come on after cranking a bit. I guess the hotter the engine, the thinner the oil and the longer I'd have to crank to get the oil pressure pressure up!!

I ordered a new relay to-day, hope to have it to-morrow. Will post again on the result, but I think I owe you a Thank You!!!

Ron ...

 

[RonJ]

Turned out the problem was in the pump. The check valve wasn't holding at all, so the pressure in the system was going to zero as soon as I shut down.

Maybe, when the engine was real hot, the heat in the fuel rail would drive the fuel back to the tank, emptying the rail. The 2 seconds the fuel relay provides wasn't wasn't long enough to fill the system resulting in a long crank to get the oil pressure to start the pump and fill the system. A pressure gauge shows the pressure trying to come up and then dropping to zero when the relay opened.

Anyways, the new pump solved the problem, it starts right up hot or cold now!! And I own a brand new pressure gauge now ...

Ron ...