engine dying - Pirate4x4.Com : 4x4 and Off-Road Forum

Murfman · 07-08-2003, 09:08 AM

i have an 87 yj with 4.2 and an mpi fuel injection kit on it. yesterday on the way wheeling, it started to loose power like it was running out of gas. we got it started and what is wierd is, if you sprayed wd-40 in the throttle body, it ran like a champ. it only does this when it is hot, about 210 on the guage. you let it cool down and it runs fine. i cleaned the k&n and changed out the fuel filter. i replaced the throttle possition sensor about 5 months ago. i have noticed a raw gasoline smell but cant find any leaks. im thinking that its running rich and that is causing the temp to go up and shutting the computer down, killing the engine. lots of gas comes out of the valve on the fuel rail, one of the first things we checked cuz of the "running out of gas symptoms" i havent been able to duplicate it since i changed the fuel filter but it hasnt been as hot either.

Old Army · 07-08-2003, 10:18 AM

Overheating will not occur from too rich a mixture. It might happen if the mixture is too lean. Assuming your temperature gauge is correct, 210 degrees is not excessively hot. It shouldn’t have an issue at that temperature. I vote for vapor lock. As I recall, the Mopar system uses an in-line fuel pump that draws from the tank. This can sometimes lead to vapor lock issues. I would invest in a fuel pressure gauge and see what happens to the pressure when it starts this again. If your pump is near anything hot, you can relocate it. Or you can install an in tank pump.

-Old Army

TexasBlake · 07-08-2003, 10:26 AM

Sounds like a bad fuel pump. I'm not familiar with how the MPI kit deals with that issue. I assume they include a high pressure pump in the kit??? Have you done a fuel pressure test?

Murfman · 07-08-2003, 05:59 PM

btt

AGGIECJ-7 · 07-08-2003, 07:28 PM

i would be willing to bet you have a vacume leak. i had the same problem with mine. i thought it was the gaskets on the carb but it turned out to be the gaskets on the intake/exhaust manifold. jeep had a shitty designe and the intake and exhaust gasket it all one piece. i have been through two of them on mine. take that WD40 and spray it around the intake manifold. if the idle goes up then you need to pinpoint the problem. the reason that it runs better with wd-40 is because with a vacume leake, too much air is getting into the combustion chambers.

hope this helps....it will be easier to check for a vacume leak before replacing parts...

07-08-2003, 09:08 AM	#1 (permalink)
Murfman Registered User Join Date: May 2002 Member # 11973 Location: Colorado Springs, Co Posts: 573	engine dying i have an 87 yj with 4.2 and an mpi fuel injection kit on it. yesterday on the way wheeling, it started to loose power like it was running out of gas. we got it started and what is wierd is, if you sprayed wd-40 in the throttle body, it ran like a champ. it only does this when it is hot, about 210 on the guage. you let it cool down and it runs fine. i cleaned the k&n and changed out the fuel filter. i replaced the throttle possition sensor about 5 months ago. i have noticed a raw gasoline smell but cant find any leaks. im thinking that its running rich and that is causing the temp to go up and shutting the computer down, killing the engine. lots of gas comes out of the valve on the fuel rail, one of the first things we checked cuz of the "running out of gas symptoms" i havent been able to duplicate it since i changed the fuel filter but it hasnt been as hot either. __________________ Only in a Jeep

07-08-2003, 05:59 PM	#4 (permalink)
Murfman Registered User Join Date: May 2002 Member # 11973 Location: Colorado Springs, Co Posts: 573	btt __________________ Only in a Jeep

07-08-2003, 07:28 PM	#5 (permalink)
AGGIECJ-7 Granite Guru Join Date: Apr 2001 Member # 4228 Location: Newark, Tx Posts: 884	i would be willing to bet you have a vacume leak. i had the same problem with mine. i thought it was the gaskets on the carb but it turned out to be the gaskets on the intake/exhaust manifold. jeep had a shitty designe and the intake and exhaust gasket it all one piece. i have been through two of them on mine. take that WD40 and spray it around the intake manifold. if the idle goes up then you need to pinpoint the problem. the reason that it runs better with wd-40 is because with a vacume leake, too much air is getting into the combustion chambers. hope this helps....it will be easier to check for a vacume leak before replacing parts... __________________ Steven W My Website 82 CJ-7 - SOA, geared, locked, 35's 02 Ram 2500 - Cummins, 4x4, 6spd

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07-08-2003, 10:18 AM	#2 (permalink)
Old Army Registered User Join Date: Nov 2002 Member # 14841 Location: Alexandria, VA Posts: 117	Overheating will not occur from too rich a mixture. It might happen if the mixture is too lean. Assuming your temperature gauge is correct, 210 degrees is not excessively hot. It shouldn’t have an issue at that temperature. I vote for vapor lock. As I recall, the Mopar system uses an in-line fuel pump that draws from the tank. This can sometimes lead to vapor lock issues. I would invest in a fuel pressure gauge and see what happens to the pressure when it starts this again. If your pump is near anything hot, you can relocate it. Or you can install an in tank pump. -Old Army

07-08-2003, 10:26 AM	#3 (permalink)
TexasBlake El Guapo Join Date: Feb 2002 Member # 9722 Location: ColoradoBlake Posts: 4,736	Sounds like a bad fuel pump. I'm not familiar with how the MPI kit deals with that issue. I assume they include a high pressure pump in the kit??? Have you done a fuel pressure test?