• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

won't start hot---fuel pump?

P

purvisdotcom

NAXJA Forum User
Location
Hawaii
My 89 MJ project. It starts up fine, can even drive it(although the clutch is whining at me with the pedal engaged, even in nuetral) but everytime after about 5-10 minutes the engine stalls out and won't restart at all. then after it cools down(maybe a half hour or more)it will start up again and do the same thing.

One thing I notice is that the fuel pump does not make any noise when I turn the key forward when the engine is hot. Is there one of the sensors that would cause this or is it just a bad pump maybe. I read in one post that when the pump starts going bad, it can shut off when hot. I guess I never really thought that the pump got very hot in the first place.

Maybe I should check the electrical signal to the pump when the car isn't starting?

Oh yeah, also my idiot light for temp is always on when the key is in, I wonder if the temp sender is bad and if so would cause this?
 
Last edited:
92DripCherokee said:
might be vapor lock in the fuel rail. Do you have the heat shield mounted to the intake manifold?
Click to expand...

I do have a heat shield between intake manifold and injectors. Is there a second one for the 2 more sucepptible injectors I wonder?

Also my engine is overheating these days, maybe its vapor locking in spite of the heat shield? Thanks I read that I can test it be checking the fuel rail when It won't start, if air comes out, thats it. I'll try not to catch on fire:flame:

Matt
 
RyanM said:
I know its what everyone first assumes, but sounds like the crankshaft sensor.
Click to expand...
Mine periodically crapped out, if I did get it to restart it acted like the MAP was unplugged (way rich and barley ran). I sometimes couldn't get it to restart until it cooled down again.
Turned out to be the CPS. When the CPS was hot it would ohm out at 292, when cold 225.
Funny it would act up the worst when the temperature was almost exactly 140 F plus or minus a few degrees. It usually ran and started OK at higher temperatures and lower temperatures most times.
 
has that got the ballast resistor on the inner fender for the fuel pump? if it does, bypass it and throw it in the trash. if not, it could be a cps issue.
 
One thing I notice is that the fuel pump does not make any noise when I turn the key forward when the engine is hot.

Yes they do have a temperature overload in the motor, you don't want a overheated electric fuel pump.
 
8Mud said:
Mine periodically crapped out, if I did get it to restart it acted like the MAP was unplugged (way rich and barley ran). I sometimes couldn't get it to restart until it cooled down again.
Turned out to be the CPS. When the CPS was hot it would ohm out at 292, when cold 225.
Funny it would act up the worst when the temperature was almost exactly 140 F plus or minus a few degrees. It usually ran and started OK at higher temperatures and lower temperatures most times.
Click to expand...
I have a piece of dookie ohm meter, I think I should get a digital. Also I suck at electrical stuff. I guess that is my next thing to learn. I think It probably is the CPS. I do have a ballast resistor, might as well do that too.

Thanks guys.

Also today I checked the pressure at the rail when it was not starting and there is about 39, so it isn't a fuel issue.
 
langer1 said:
One thing I notice is that the fuel pump does not make any noise when I turn the key forward when the engine is hot.

Yes they do have a temperature overload in the motor, you don't want a overheated electric fuel pump.
Click to expand...

do you mean that the pump will not go on when a certain temp is reached? and that the sensor is in the fuel pump itself? I never knew that.
 
Thats what I mean, it's called a thermal overload, you don't want a bad fuel pump motor to get overheated in your fuel tank.

You said you don't hear the pump when you have the problem and just letting it set and it starts, I say change the pump.
 
Did my CPS today I was having the exact same problems. I borrowed a code reader and mine was throwing a code that told me it was the CPS even though I never got a check engine light. She starts fine now even when hot.
 
I am going to get a cps, but I also decided not to put it in until I get the clutch changed out. it is actually vibrating the bell housing and no doubt heating up in the process, I bet thats why my current cps died and I don't want to subject another one to that.
 
Just had the same problem with my 88 cherokee. On mine my fuel line where it came off the injector rail was contacting the edge of the intake manifold and then going down thru a bracket on the side of the engine. seems the new gas(10% ethanol) was reaching boiling point then causing a vapor lock in the intake. once it cools off the vapor lock went away. I removed the bracket that held the fuel line against the side of the block and used a zip tie looped over the brake booster bolt to hold the fuel line up and off the intake manifold. Haven't had a stall since.:roll: Hope this helps.
 
bpatrick54 said:
Just had the same problem with my 88 cherokee. On mine my fuel line where it came off the injector rail was contacting the edge of the intake manifold and then going down thru a bracket on the side of the engine. seems the new gas(10% ethanol) was reaching boiling point then causing a vapor lock in the intake. once it cools off the vapor lock went away. I removed the bracket that held the fuel line against the side of the block and used a zip tie looped over the brake booster bolt to hold the fuel line up and off the intake manifold. Haven't had a stall since.:roll: Hope this helps.
Click to expand...

holy shnapps, mine is like that too. I'm going to try it and see if it goes. The reason I never changed it is I looked and it was the stock place for the fuel line.
fuelline.jpg

I'll let you know if it fixes it
 
You must log in or register to reply here.

Similar threads

N
New Engine is Hard to Start
Replies
0
Views
34
NGThomas
N
V
High temp woes
2
Replies
21
Views
413
Vitzaa
V
Ecomike
87 Renix XJ No fuel, No brake lights, cranks fine
2
Replies
27
Views
862
Anak
Anak
Z
RENIX fuel delivery questions
Replies
4
Views
336
Ecomike
Ecomike
R
Bound up torque converter. Aw4 pump replacement
2
Replies
21
Views
3K
RCP Phx
R
Back
Top