It died on me..

[bigred4x4]

Hey guys quick senario would like some opinions. ok so, pulled in got gas, went to pull out and when accelerating about the end of 2nd gear the engine drops out. No power like it just was being choked out, slowed down and pulled over by the time I stopped the engine finally died. Went to restart and it was like it was running on fumes. A second of choking,sputtering then quites. Waited about ten minutes and she fired right up and I drove the rest of the way home with no issues. Checked scanner live data on the ride and everything was normal.

I'm wondering if this is related to when I was 4 wheeling a few weeks ago it pretty much did the same thing. And waited and fired up without any more problems until now.

I'm guessing fuel pump maybe, but is this typical? Any other suggestions? I feel one day it won't restart once it dies until something gets replaced.

Not really looking forward to dropping the gas tank if that's what it is.

Do these engines ever have vapor lock issues?

Fuel filter replaced about two years ago

 

[Runnin'OnEmpty]

If no codes are showing up, then I'd suspect the fuel pump. Your symptoms are typical of when they are starting to fail. The brushes on the pump motor wear out.

I cut a hole under the left rear seat to access my pump. For me, that was easier than working underneath the vehicle. There's a post here that shows where to cut the access hole.

 

[BKennedy]

I replace my fuel filter yearly.
Did you check the fuel pump relay? Swap it out with one of the ABS relays in the power distribution box under the hood and see if the ABS light comes on. I had the same issue several years ago and it was the relay. I am still running the original fuel pump.

 

[bigred4x4]

Yes the relay has had some Trouble for some time now sometimes the fuel pump won't prime and I have to wiggle the relay with the key turned to prime the pump might do it for a week or two then disappear for awhile, replacing the relay has no change, and I've never had fuel problems once I've got it started been doing this for years except now the wiggle trick doesn't seem to work so I'll try to swap it out does the relay affect the fuel pump power while the engine is running?

Also when monitoring live data one thing I noticed I thought was strange was the ECT reading was fluctuating from about 185 to 208 it would drop to 185 then climb to 208 and repeat this cycle over and over the entire drive and would complete this cycle about every minute. Not sure if this is a problem or normal.

 

[96eb96]

Also when monitoring live data one thing I noticed I thought was strange was the ECT reading was fluctuating from about 185 to 208 it would drop to 185 then climb to 208 and repeat this cycle over and over the entire drive and would complete this cycle about every minute. Not sure if this is a problem or normal.

Kinda Normal for our v6es. I have a feeling there is a steam issue from tiny cracks in the heads. Monitor your misfire counts too.

 

[BKennedy]

Have you tried to fix the problem with the relay wiring? If you have to wiggle the relay to get it to run, you have a loose connection in the wiring at the relay plug. I would fix that before I replaced a fuel pump.

 

[bigred4x4]

It did it again earlier. it started fine but ran rough for a second. Ran fine going to the shop to pick up my other car and it was choking again in the parking lot upon restart then waited a minute and fine again. I'm going to check fuel pressure ASAP. The wiring issue does need attention but have never had an issue While running, only the priming until recently. I'm willing to bet on the fuel pump at this point but do want to do some other tests before I go ahead and order one. Was considering a Bosch my father in-law replaced a few cheapos in short order before buying a Bosch for his bronco 2 and hasn't had a problem since.... But If there is something better you know of I'll take it into consideration.

I had the motor apart not too long ago I paid careful detail refreshing the heads and didn't see any cracks but I guess a magnaflux would be the only true test if they are super small. But then again I just repaired a heater hose leak and topped off the Reservoir maybe trapped air? I know these systems can take awhile to rid all the trapped air via the owner's manual.

 

[96eb96]

It did it again earlier. it started fine but ran rough for a second. Ran fine going to the shop to pick up my other car and it was choking again in the parking lot upon restart then waited a minute and fine again. I'm going to check fuel pressure ASAP. The wiring issue does need attention but have never had an issue While running, only the priming until recently. I'm willing to bet on the fuel pump at this point but do want to do some other tests before I go ahead and order one. Was considering a Bosch my father in-law replaced a few cheapos in short order before buying a Bosch for his bronco 2 and hasn't had a problem since.... But If there is something better you know of I'll take it into consideration.

I had the motor apart not too long ago I paid careful detail refreshing the heads and didn't see any cracks but I guess a magnaflux would be the only true test if they are super small. But then again I just repaired a heater hose leak and topped off the Reservoir maybe trapped air? I know these systems can take awhile to rid all the trapped air via the owner's manual.

Make sure you have new relays too for your FP and PCM, I change them at 100K or so for PM, had issues with that on other Fords. At least keep a spare.

Local machine shop said they don't touch old 4.0OHV heads, 8/10 times there are cracks, or soon to be cracks. You can get a new loaded set for under $400.

Trapped air will do it, but it will bleed out after a few drive cycles. Open your rad cap, and observe if the coolant rises. If it does you may have a cracked head. Also individual misfire counters can give a clue.

 

[bigred4x4]

I think my engine only sets a misfire with the interruption of spark iirc. I'm going to test the connections, relay , and fuel pressure, and the pressure regulator it would be awesome if it wasn't the pump but I'll find out shortly.

As far as the relay I always found it strange how sometimes it wouldn't prime because of bad relay connection but would never have problems once running does the relay stay on the whole time? Or is it just for priming.

Also would a cracked head cause an internal loss of coolant?

 

[96eb96]

I think my engine only sets a misfire with the interruption of spark iirc. I'm going to test the connections, relay , and fuel pressure, and the pressure regulator it would be awesome if it wasn't the pump but I'll find out shortly.

As far as the relay I always found it strange how sometimes it wouldn't prime because of bad relay connection but would never have problems once running does the relay stay on the whole time? Or is it just for priming.

Also would a cracked head cause an internal loss of coolant?

No, the misfire monitors don't care about the cause of the misfire. Could be spark, fuel, compression, etc. It looks at your crank wheel and measures the timing between the teeth. A misfire slows things down, and it accounts for the position of each tooth so it can pinpoint the misfiring cyl. If you look at your wheel there is a missing tooth for indexing. You could have plenty of misfires and not set any code. There is an allowance for the calibration (a truck may be allowed to pollute more vs a car). It is pretty sophisticated, they were using machine learning back in 96 to accomplish this.

The misfire counts are reset when you start up your truck. There are tons of PIDs that most scan tools won't see. The PCM even computes Torque very accurately. Goes up to about 215 on our engine. Never got it to 220.

Relays could cause lots of strange issues. Over time they create a high resistance carbon contact point and lower the voltage, it may cause it to cross a threshold and just not work. A bad PCM relay will not make the CEL come on, and you just won't start. Yes, these relays are always on.

If you are losing coolant internally (freeze plugs and intake gaskets could be a culprit too) you have combustion chamber to coolant system cracks. A bit off coolant enters the cyl and causes a misfire here and there. You also lose compression thru the crack.

 

[bigred4x4]

I've tested compression and and I'm not losing coolant, also rebuilt engine about two years ago so all the gaskets are new I'll start from the relay side and go from there, the only time it's thrown a misfire code is when I had a cracked spark plug but I guess that's not a for sure thing that it still isn't doing it from time to time. What other symptom would be present for a bad PCM relay?

 

[96eb96]

cracked plug (if internal) could be from a bit of coolant, maybe not.
Bad PCM relay usually causes a no start, or even a stall. Bad FP relay could deliver lower voltage to the pump, drop out, etc. Good to look at the whole circuit before you replace the pump. Real techs can put a current clamp on the wire, look at the motor draw waveform.

 

[bigred4x4]

Any suggestions on say if it was the contacts in the power distribution box how would I go about fixing that.

 

[96eb96]

Any suggestions on say if it was the contacts in the power distribution box how would I go about fixing that.

Voltage drop across the wire,
Wiggle tests.

I can describe more if necessary

 

[bigred4x4]

Turdle got with me and explained how to access the contacts I'm going to try that and see what I find I'll try to take pics too. Hopefully I can get to that tonight after work.

 

[96eb96]

Turdle got with me and explained how to access the contacts I'm going to try that and see what I find I'll try to take pics too. Hopefully I can get to that tonight after work.

Would be nice to see voltage at the pump, but unfortunately you have to drop the tank. I would almost be tempted to cut a hole on a truck this age.

 

[bigred4x4]

I was referring to the contacts inside the power distribution box.

 

[BKennedy]

I was referring to the contacts inside the power distribution box.

I would start with that. Its the easiest to get to, and you know there is a issue. You can pop the tabs on each end of the power distribution box and turn it upside-down to see the wires. Looked for a wire coming loose at the fuel pump relay. You can also bend the contacts points inward at the relay plug to get a better grip on the relay. Disconnect the battery before you do this, the power distribution box has constant power.

 

[koda2000]

Would be nice to see voltage at the pump, but unfortunately you have to drop the tank. I would almost be tempted to cut a hole on a truck this age.

There should be an electrical connector on the inside of the frame rail, just over the driver's side rear axle. Remove the left rear tire to get access to it. You can push out the clips that hold the wiring harness to the frame and unplug the fuel pump connections. From there you can test for power to the fuel pump w/out dropping the tank.

 

[bigred4x4]

Ok so I took apart and cleaned the contacts on the power distribution box and I swapped the W.A.C relay with the fuel pump relay ..... What is the w.a.c anyway?

Bent out prongs on relay and it fits much tighter and doesn't feel loose any more.I also tried the key a few times and got a prime every time.

Its too late to fire it up, but tomorrow I'll do a fuel pressure test and a drive and report back.