runs for a sec then dies

Dexter350k · 02-10-2007, 12:35 PM

i have an 88 cherokee......with yet ANOTHER problem..... just died on me when i was driving..... now i start it and it revs itself up to 2000rpms and then just dies... when i push the pedle nothing happons it wont move at all but it starts everytime and dies.... anyone have anyidea what would be causing this??

kg4kzv · 02-10-2007, 12:47 PM

Check the ballast resistor on the drives side fender you may need to jump it out to check it but might be unplugged.

Chris

Dexter350k · 02-10-2007, 02:25 PM

ill try that and see what happons

Dexter350k · 02-10-2007, 05:31 PM

well that didnt work.....thanks for trying.... anyone else know what i should do?

se7vn · 02-10-2007, 05:47 PM

Check for leaks around your fuel rail, sometimes, it can get a little to start up but looses pressure too fast to stay running, mine did the same thing for the longest time and come to find out, that was the problem. I tried all the resistors, fuel pump, vaccum leaks, after you start it each time, purge the fuel rail and see if any comes out, mine would just drip out, then sometimes it would spray out. So check for leaks!! Doesn't matter how much it's leaking, if it's leaking, then you're losing that pressure to keep it running, good luck!...

kg4kzv · 02-10-2007, 06:16 PM

Also check fuel pump fuse and relay.

Chris

Dexter350k · 02-10-2007, 08:07 PM

i messed around with it a little more and reailized i dont hear the fuel pump kicking on when i turn the key on.... so my guess is its the sending unit relay or fuel pump itself.... ill check for leaks tomarrow.... i guess we will find out sooner or later

se7vn · 02-10-2007, 08:47 PM

Well, sometimes the pressure in the fuel system can still be in there after you hear the fuel pump kick on maybe 1 out of 3-5 times. It'll only prime up if there's no pressure left. Try turning the key to the on position, then off, on then off very slowly, then see if that works, if it does then it's your fuel pump on it's way out, but if it doesn't, then you're not keeping pressure for some reason, (ex. A leak somewhere)

tangofox007 · 02-10-2007, 09:09 PM

Quote:

Originally Posted by se7vn

Well, sometimes the pressure in the fuel system can still be in there after you hear the fuel pump kick on maybe 1 out of 3-5 times. It'll only prime up if there's no pressure left.

How does it know? There is no fuel pressure sensor.

se7vn · 02-10-2007, 09:10 PM

If there's already pressure in the system, it can't add more.....

tangofox007 · 02-10-2007, 09:56 PM

Quote:

Originally Posted by se7vn

If there's already pressure in the system, it can't add more.....

That won't stop the pump from running. If there is no fuel pressure sensor, how does the pump know if there is pressure or not?

Marge · 02-10-2007, 09:58 PM

I have a 2001 Cherokee Sport and it is leaking something, possibly transmission fluid. Can I drive it?

se7vn · 02-10-2007, 10:28 PM

Dunno how it works, but that's what I was told when mine was going, there's thread on this forum about it somewhere..

tangofox007 · 02-10-2007, 10:42 PM

Quote:

Originally Posted by se7vn

Dunno how it works, but that's what I was told when mine was going, there's thread on this forum about it somewhere..

When the key is placed in the run position, the ECU powers the fuel pump for 1-2 seconds, then shuts it off (whether there is adequate pressure or not) until the key is moved to start. There is no feedback to the ECU (or anything else) with regard to fuel pressure.

kg4kzv · 02-11-2007, 11:20 AM

tangofox007 Gets the prize here so here it is a

. The ECU gets no input for fuel pressure. The fuel pressure regulator is mechanical and sends excess pressure and fuel back to the tank. That is why low or no fuel pressure won't trigger a light or code. My understanding of the system on the older fuel injected XJ's is that when the key is first turned to start a relay triggers and bypasses the ecm for a few seconds to pressurize the fuel system. Then once the ecm gets inputs from other sensors like the crank or distributor that the engine is running it triggers the relay to run the pump and include the ballast to quieten the pump. At least that is how I understand the way it works.

Chris