Jeep Cherokee Talk banner
1 - 12 of 12 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter · #1 ·
Occasionally, subject to no pattern that I can detect, it seems like fuel stops flowing to the engine. So, for example, while driving and using the accelerator, suddenly the engine stops getting fuel, and the rpms and oil pressure drop. Generally, if you keep pushing the gas, the flow returns and the vehicle functions normally, until it happens again. If the flow doesn't return quickly, then the engine will cut off. Generally when that happens, the engine will crank again with no problem. This has happened at idle and while moving. When I say "the engine stops getting fuel", I am not positive that is what is actually happening. I mean that is what it seems like. Not getting fuel, fuel not being ignited, something like that.

I just had the following replaced: crank position sensor, distributor pick-up, fuel pump, and gas tank (and whatever gas was in it). And it did it again. So, if it is not any of the things that were just replaced, what could it be?

FYI, the reason I replaced the fuel tank was that it was a steel tank, and the vehicle sat and was neglected for about two years, so I thought maybe rust/sediment in fuel. But I have driven the vehicle for about 8 or 9 months after resurrecting it from its two-year neglect. This issue arose only recently. Whatever the problem is, it was not a problem for 6-7 months.

Also FYI, I did the usual fuel injector upgrade. But this problem didn't arise until months after that. It runs very nicely with the new injectors. Anyway, I don't think it has anything to do with the injectors, but am open to any suggestions anyone may have.
 

·
Super Moderator
Joined
·
13,505 Posts
it's tuff to say. I would look for the ground wire for the fuel pump, make sure where it attaches to the body is not rusty/corroded. Also, if you have the ability to monitor the TPS, log it and if see if the readings are erratic.
 

·
Registered
Joined
·
11 Posts
Discussion Starter · #3 ·
it's tuff to say. I would look for the ground wire for the fuel pump, make sure where it attaches to the body is not rusty/corroded. Also, if you have the ability to monitor the TPS, log it and if see if the readings are erratic.
Any idea where the ground for the fuel pump is? The entire wiring harness from the fuel pump goes inside the body a short distance from the fuel pump, so I guess the ground must be under the hood somewhere? Also, any reason not to replace the fuel filter if I have no idea when it was last replaced, if ever?
 

·
Super Moderator
Joined
·
13,505 Posts
the fuel filter should be along the frame near the lr fender well. The fuel pump ground is inside the cargo area. on the driver side. behind the spare tire.
 

·
Registered
Joined
·
11 Posts
Discussion Starter · #8 ·
I replaced the TPS yesterday, and have driven it a few times. It cut off again on my most recent trip. I was braking to make a turn (so, not giving it any gas), and it cut off. I completed the turn without power steering, stopped, cranked it, and it cranked right back up and made it home. Also, it seemed to "lurch" a few times during these few trips while giving it gas. Any more ideas? I am about to give up and take it to the Jeep dealer in the hope that they have an old-timer who knows XJs inside and out.
 

·
Super Moderator
Joined
·
13,505 Posts
When replacing sensors, it is sometimes advantageous to reset the ECM to factory specs. You can do this by pulling both battery cables, touching them together for about 30 seconds. then reattached. This will drain the capacitors and reset it's memory. The ECM will then start to relearn all the sensors. Overtime your sensors can get out of whack and the ECM will compensate for it to basically keep running, But if you don't reset these sometimes you can get less than optimum performance.

One other thing. Check the wiring around the back of the motor. The wire loom going between the valve cover and firewall, will rub against one of the valve cover bolts and short out. causing all kinds of random head scratching infuriating problems.
 

·
Registered
Joined
·
11 Posts
Discussion Starter · #10 ·
I reset the ECM and I'm still having the problem. I eyeballed the wiring harness around/behind the engine, and saw no obvious problems. But anything electrical is beyond my ability to diagnose or repair, so a short definitely remains a possibility. But I have a new theory. My theory is that the temperature of the engine has something to do with triggering the problem. After I reset the ECM, I drove to the store. It did fine at first, but after a while, with the engine up to normal operating temp and me driving about 55 on a main road, it started having the loss of power again. And once it starts, it doesn't stop doing it. And I believe that is how this problem has been all along. I.e., the vehicle runs fine for a little while (while the engine is cool), then it starts having the problem, and once it starts it keeps doing it. So, on the way home from the store, I blasted the heat to keep the engine cool, and I accelerated as little as possible and coasted as much as possible - again, to keep the engine temp as low as possible. And I don't think it lost power the entire way home. See pic of temp gauge below. That is as high as the temp got on the way home. So, does this tell you anything about what the problem may be?

Probably unrelated, but I should mention that early this year I replaced the crappy "dummy light" instrument cluster with the full instrument cluster. As a result I had to replace the temp sending unit on the back of the engine. While doing that, the connecter became damaged, and I had that replaced March 3. This problem of loss of power didn't begin until June. Pic of the new sending unit, connector and wire are below.

Automotive tire Gas Tread Auto part Synthetic rubber

Speedometer Odometer Trip computer Tachometer Gauge
 

Attachments

·
Super Moderator
Joined
·
13,505 Posts
changing the cluster does make a difference. The REAR temp sensor and oil pressure sensor need changed to sending units. this is for the gauges in the cluster to work. The old sensors are just on and off switches. The front temp sensor on the t-stat housing is also a sending unit and is what the ECM uses for its engine temps. If that sensor is bad it could cause the engine to stay in closed loop. when the engine is cold it runs in closed loop, meaning it does not use input from the other sensors,, such as o2. once up to temp it starts taking input from the sensors, then makes adjustments to the fuel trims. You may want to scan your o2 sensors and make sure they are functioning proper. also, I have seen the o2 sensor wire get melted on the exhaust.
 

·
Registered
Joined
·
11 Posts
Discussion Starter · #12 ·
Turns out the problem was the coil. Not the coil itself, but the electrical connector to the coil. The plastic area where the connector connects to the coil was broken (and jury-rigged with a zip tie), and the connector was shorting. Replaced the coil. Runs fine now. So now I'm wondering what idiot jury-rigged the connector with a zip tie.
 
1 - 12 of 12 Posts
Top