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91 Explorer Startup Diagnostic Help?

burkjt

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February 3, 2011
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Year, Model & Trim Level
91 XLT
I have a 91 explorer that has had some issues starting lately. The truck will occasionally refuse to start, but will eventually turn over with enough cranking. When it refuses to start it will crank at normal speed, and fire occasionally until I try to start it several times (like 3 or 4 sessions of 5 - 10 seconds of cranking). After it starts, it will start fine for several days.
It has very low power output. I could never get it over 3500RPM. I have ran a couple cans of injector cleaner, and had them washed at walmart. After the walmart was, I was able to get it to 4200 RPM for a day or 2, but it dropped back to 3500 gradually. The injectors all read the proper resistance on there terminals.

Today, we had a cold spell along with the rest of the country. The truck refused to start this morning and all of the day. It warmed up a little and I managed to get it started. It seemed to be putting out a bit more steam than normal, even after being warmed up. While it was warming up it hesitated when I gave it gas.

I am back to suspecting the injectors or something fuel related. Any input would be appreciated.
 



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bad fuel pump. new pump is about $80 (i just replaced mine, *exact* same symptoms)

replace the fuel filter while your at it.
 






I replaced it about a year ago..I suppose that the clogged injectors could have killed the new one in that time.
 






I replaced it about a year ago..I suppose that the clogged injectors could have killed the new one in that time.


Negative - fuel pressure is a loop from the pump>filter>regulator>back to tank.

the fuel pump should see a solid 40psi weather your injectors are firing or not. it's regulated by the regulator, excess pressure bleeds off in the return line to the tank only a very tiny fraction of the fuel pumped actually gets injected into the engine.

did you replace the filter when you installed the new pump? have you measured your fuel pressure? it is possible that your new fuel pump was a dud (or poorly made pos that went bad right away) what brand fuel pump was it? what auto parts store did it come from?

BTW "clogged injectors" are a bit of a myth.
 






I changed the filter about a week after the pump. The pump came with the car when I got it. I cant remember the brand, but I suspect that it was cheap. I am planning on getting a pressure reading tomorrow.

On the clogged injectors- They were clicking very loudly for the first 5 minutes of running. After the injector cleaning they stopped doing that. Any thoughts as to what that could indicate?
 






I changed the filter about a week after the pump. The pump came with the car when I got it. I cant remember the brand, but I suspect that it was cheap. I am planning on getting a pressure reading tomorrow.

On the clogged injectors- They were clicking very loudly for the first 5 minutes of running. After the injector cleaning they stopped doing that. Any thoughts as to what that could indicate?


It's probably not the injectors you were hearing clattering, it was probably the rockers (aka lifter tick, push rod clatter, etc) the reason it stopped is because the engine oiled up, and warmed up, and they got quieter. I've never heard any audible sound from an injector.

what weight oil are you running? you should be running 10w30 or if your in freezing cold weather, 5w30. remember lower viscosity oil lubricates faster, especially when cold. (and keep additives like Lucas out of the engine)

injectors very, very rarely fail, and I've never had an issue from a "clogged" injector. it seams most of the time when injectors fail they leak (black smoke on start up, runs too rich, etc)
 






It has 5w in it now. The clattering was persistent, for months. It would last for about 5 minutes to a half hour, every time the car was started after being off for more than 3 or 4 hours. When you felt the braided fuel hose that connects to the rail, it felt like it pulsed with the clicking, was not engine wiggle. Very distinct.
 






It has 5w in it now. The clattering was persistent, for months. It would last for about 5 minutes to a half hour, every time the car was started after being off for more than 3 or 4 hours. When you felt the braided fuel hose that connects to the rail, it felt like it pulsed with the clicking, was not engine wiggle. Very distinct.

Hmm.. interesting.

I'd say check fuel pressure and report back. Fuel pressure readings (And how fast the pressure comes up when you turn the key) will shed a bit of light on the problem.

is it throwing any codes.. check engine lights etc?
 






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