The Comanche has failed me

[hgeranium]

randomly noticed a huge oil leak from the back of the engine. Back at the valve cover had oil, most things on the distributor side had oil (none in distributor), head/block/trans COVERED in oil. This was in the middle of a 180 mile road trip. I make it  after adding oil and then it does this not long after getting into town. The video is me flooring it going about 5 miles an hour. 
 

In park it will rev all day long and it idles OK. In gear it won’t rev past 1500-1800 and bog down/slowly start to die even when flooring it. Actually got stuck on the side of the highway because I literally could not accelerate. It would just want to die and I had to put it in reverse back into the shoulder. Waiting a long time randomly fixed the acceleration problem. That sound feels like a spark issue but that plus the oil could be what? It’s not the distributor since inside the cap was bone dry. This problem came out of nowhere. I suppose the oil and acceleration problem could be independent but I feel like it’s an unlikely coincidence. 

[hgeranium]

It’s a problem that’s somehow connected to heat. After letting it sit for a few hours it drives great until it’s warmed up for  a while. 

[Pete M]

fuel pump dying?  have you accomplished all of cruiser54's MJ tips yet? 

[hgeranium]

33 minutes ago, Pete M said:

fuel pump dying?  have you accomplished all of cruiser54's MJ tips yet? 

Most of them. Not the fuel pump ground yet. And that still wouldn’t explain the oil. My first thought is maybe the coil is going bad and getting hot. I had to leave the Comanche and borrow a car to get back home last night, so I won’t get to look at it until Thanksgiving sadly. 
 

i’m trying to think what would cause all that oil spray in the back of the motor and it could really only be a few things, none of which really relate to the drivability issues. The oil happened before the driving problems, so maybe the oil itself is fouling something up? I don’t know if oil getting all over the CPS would do something or not. It’s just hard me not being there. Best I can do is be prepared to know what to look for. 

[Eagle_SX4]

Listening to the video its sounds like the engine is okay. Some pics of where the oil is would help but it is most likely a bad valve cover gasket.

 

I am with Pete on this one check your fuel pump. Sometimes when fuel pumps die they die slowly and seem okay when cold but worse when hot.

[speeding_infraction]

Any chance you just did a valve cover gasket recently?

[hgeranium]

26 minutes ago, speeding_infraction said:

Any chance you just did a valve cover gasket recently?

 

33 minutes ago, Eagle_SX4 said:

Listening to the video its sounds like the engine is okay. Some pics of where the oil is would help but it is most likely a bad valve cover gasket.

Done ~10,000 miles ago about 10/2022. In hindsight I definitely didn’t do the correct tightening order. VC is bone dry up front but still leaked from the back. Yall think the oil could be a red herring for the FP issue? Also how could I go about testing the pump (without taking the bed off/dropping tank and other than getting that FP ground). Fuel pressure looked good from the schrader valve if that matters. 

[hgeranium]

Just now, hgeranium said:

 

Done ~10,000 miles ago about 10/2022. In hindsight I definitely didn’t do the correct tightening order. VC is bone dry up front but still leaked from the back. Yall think the oil could be a red herring for the FP issue? Also how could I go about testing the pump (without taking the bed off/dropping tank and other than getting that FP ground). Fuel pressure looked good from the schrader valve if that matters. 

The oil spray had gotten significantly worse on that road trip. It was dripping tons of oil which it never did before. All my stuff on the distributor side got a nice little film of oil on it. Ignition wires, dizzy cap, coolant bottle, vacuum canister etc. The firewall behind the VC is completely black now too. Could the VC have just catastrophically failed suddenly like that? 

[Eagle_SX4]

1 minute ago, hgeranium said:

Fuel pressure looked good from the schrader valve if that matters. 

Did you test the pressure with a gauge or did gas spray out when you depressed the valve? 

[hgeranium]

2 minutes ago, Eagle_SX4 said:

Did you test the pressure with a gauge or did gas spray out when you depressed the valve? 

The latter. A very fine mist. This was on the side of the highway and I was desperate for clues.

[Eagle_SX4]

Defiantly check with a fuel pressure gauge. Even a poorly working pump will get some pressure up to the fuel rail.

[89 MJ]

The oil pressure sender is right there by the dizzy. That could be your oil leak. 

[hgeranium]

1 hour ago, Eagle_SX4 said:

Defiantly check with a fuel pressure gauge. Even a poorly working pump will get some pressure up to the fuel rail.

Any clue about what pressure I should be looking for? I’m thinking I drive it around somehow with the gauge hooked up, then look for a FP drop when it bogs down like that. Unless I should see a pretty big discrepancy on the gauge even at warm idle. 

[Eagle_SX4]

6 minutes ago, hgeranium said:

Any clue about what pressure I should be looking for? I’m thinking I drive it around somehow with the gauge hooked up, then look for a FP drop when it bogs down like that. Unless I should see a pretty big discrepancy on the gauge even at warm idle. 

You should see 31 psi at idle and 39 psi with the vacuum line on the fuel pressure regulator removed.

[hgeranium]

20 minutes ago, Eagle_SX4 said:

You should see 31 psi at idle and 39 psi with the vacuum line on the fuel pressure regulator removed.

I’m going to preemptively order some parts for when I’m back with the jeep on thanksgiving. Even if it isn’t the issue I want to replace the fuel pump and assembly so I know it’s good. That’s one of the few things that I haven’t replaced on the truck. I wouldn’t be surprised if my tank was absolutely varnished to hell with how horribly my fuel filter failed a few months ago. 
 

Any recommendations on a quality assembly? I’m seeing a Delphi that looks decent. 
 

So far, I’m going to order a new fuel filter, fuel pump assembly, valve cover gasket, and PCV grommet while I’m there. 

[Eagle_SX4]

MTS is the only company I am aware of that make a new sending unit. 

 

http://www.mtscompany.com/sendingunits.htm

 

They don't take online orders you need to call them. I have one in my truck and it works well. I got the version with the included pump but have already switched it out. I used a Bosch 69302 to replace it and would recommend you find one of those pumps. They have been discontinued but I found mine on eBay.

[Tex06]

Where ya located? I've got all the tools to diagnose this. 

[hgeranium]

1 minute ago, Tex06 said:

Where ya located? I've got all the tools to diagnose this. 

The truck is in San Antonio, but I'm in College Station 'til Thanksgiving sadly. I greatly appreciate the offer though

[hgeranium]

14 minutes ago, Eagle_SX4 said:

MTS is the only company I am aware of that make a new sending unit. 

 

http://www.mtscompany.com/sendingunits.htm

 

They don't take online orders you need to call them. I have one in my truck and it works well. I got the version with the included pump but have already switched it out. I used a Bosch 69302 to replace it and would recommend you find one of those pumps. They have been discontinued but I found mine on eBay.

"1986-1990 Jeep Comanche MJ 18 & 23.5-Gal. "Side Mounted" fuel tank sending unit with the 4.0L I6 fuel injected engine. This unit includes the in-tank fuel pump. Includes new lock ring, gasket and an in-tank fuel filter. "

 

I'm only seeing options for an 18 and a 23.5gal size, but mine is a 16 gallon. Is this just an error of the listing or do they not have the one that I need? And would you recommend just getting a bosch pump out the gate and order the assembly that does NOT come with a pump?

 

EDIT: Doing some research and apparently the short beds ALL came with an 18 gallon tank? It sure doesn't seem like it. I usually get about 10 miles a gallon and get about 160 miles of range. It starts dying on me if I let it get to about 145-150 miles. Unless the tank was replaced with a smaller one but I doubt it. (per Pete: )

 

[Eagle_SX4]

Long bed 16 and 23 gallon tanks are the same the only difference is the vent tube inside dictating how much fuel goes into the tank.

 

If you can find one I would definitely go with the Bosch fuel pump over a stock replacement. It is a newer design that runs quieter.

[hgeranium]

1 minute ago, Eagle_SX4 said:

Long bed 16 and 23 gallon tanks are the same the only difference is the vent tube inside dictating how much fuel goes into the tank.

 

If you can find one I would definitely go with the Bosch fuel pump over a stock replacement. It is a newer design that runs quieter.

Ok cool so that one should work. And I found one on ebay  for $72. If I'm doing this job it's getting done right.

 

Actually doing the job is another thing I wanted to pick your brain about. The truck has about half a tank of gas. I feel like I read somewhere that it's easier to pull the bed rather than the tank because there's more things you have to remove to get enough clearance for the tank to drop. If I'm totally wrong then I'm all ears. I want to make this as easy on myself as possible.

[Tex06]

I dropped my tank (23 gal long bed). Not too difficult.

[Ωhm]

Eliminate the Fuel Pump Ballast Resistor as being your problem. Bypass it.

[hgeranium]

29 minutes ago, Eagle_SX4 said:

MTS is the only company I am aware of that make a new sending unit. 

 

http://www.mtscompany.com/sendingunits.htm

 

They don't take online orders you need to call them. I have one in my truck and it works well. I got the version with the included pump but have already switched it out. I used a Bosch 69302 to replace it and would recommend you find one of those pumps. They have been discontinued but I found mine on eBay.

Bad news. Just called them and they're backordered til after the new year. Something about re-engineering the part. They're just getting names and numbers for when the part is available.

[hgeranium]

Just now, Ωhm said:

Eliminate the Fuel Pump Ballast Resistor as being your problem. Bypass it.

Already done!