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240 Hard start while warm, RPMs sometimes drop in gear

Johnnya101

Member
Joined
Jul 12, 2017
Hi all,

Noticed my 1991 245 started to not want to start when warm from running within a few hours, unless you pumped the gas pedal a little bit. Once going, I had to hold it in a little and slowly ease out so it did not stall, and after a few seconds of this, it ran fine. From what I have looked at online, this seems to be a bad fuel pressure regulator?

It also has an issue where randomly the RPMs drop like the car will stall when switching from drive to park. This has only happened more recently, and only a few times. The RPMs only drop for a second before they go back to normal.

Could this be related to the regulator, if that was the culprit? Plan on having my mechanic clean the IAC too, he seems to think that might be part of the issue.

Distributer cap has been changed, plugs and wires were done a few thousand miles ago, no engine codes. This only started happening this year after pulling it out of storage. Ran with only ethanol free premium.

Also, doesn't seem to be at all related to a failed in tank pump. Does it if tank is full or low.
 
I would carefully check for vacuum leaks. Also remove the hose between the throttle body and the mass air sensor. Check it carefully for cracks on the bottom of the hose. Check around the injectors for vacuum leaks and the intake gasket.

What is the spark plug gap? A lot of plugs don't come from the store with the correct gap of .028".

Fuel filter replaced recently?
 
The usual cause of a hard start on a warm engine that sat for a short while is a failing fuel pump check valve.

I've replaced it a couple times over the years to correct this problem.
 
Thanks for the input. I'll tell them and see what they find. There HAS been a leak by the main fuel pump, which was replaced along with the filter last year. Wonder if that could be related to the check valve going...

Not sure on plug gap, but I know it was fine with the current plugs for the past year or two.

I also forgot to mention there is sometimes a kind of delay of some sort if you have the gas pressed down a bit, and remove your foot while cruising quickly. Car kind of jumps to a lower RPM too quick. Not transmission... hard to explain.

Will definitely post updates on this.
 
I think both of you were right. Bad fuel pressure regulator with disintegrated hose letting air in, and also a bad fuel regulator and possibly bad/leaking main fuel pump all in one. Back to normal now!
 
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