difficult to start and stalls

[86customanche]

92 4.0 std

 

It ran fine in July then sat for a few weeks. Then it was very difficult to start and ran VERY rough, sounded like missing cylinder.

Anyway, plugs and wires and distributor cap and rotor and O2 sensor replaced.

I checked all hoses that appear to be vacuum related and they seem ok.

I cleaned the idle air control valve, it was very dirty.

 

Yesterday, after multiple long cranking sessions it started, and idled for a few minutes. Touching the peddle resulted in a stall. A little later after long cranking session, it started and I was able to run at 2500+ rpm for a few moments, followed by a stall.

After it runs awhile and stalls, I can unplug the football size vacuum thing and it hisses a little bit.

 

Today I couldn't get it to start.

 

After a long cranking session, quickly checking the fuel valve resulted in no pressure. Turning the key to on, I could hear fuel returning to tank.

 

What next?

 

edit....  I'll check the ground near the rear taillight, and try to determine if fuel pump is running.

 

 

(standard disclaimer... Dad borrowing son's Comanche Club account, while charged with running the Comanche every few weeks while son is out of state)

Edited August 18, 2015 by 86customanche

[1989 Eliminator]

I would try to actually get a fuel pressure reading off of the fuel rail to see if the fuel pressure stays constant and does not drop out. Should be around 40 psi.

 

Make sure the intake/exhaust manifold bolts are tight because this would cause a vacuum leak if they are loose.

 

Check the small vacuum hose coming from the throttle body to the MAP sensor on the firewall. If this hose is broken, cracked, or is not connected then this would cause idle and running issues.

 

Make sure ALL the grounds are clean and have a good tight connection and contact. Grounds are located: Middle of the firewall (braided cable should be replaced with a proper thick cable), dipstick ground. I would also add a few ground wires to upgrade the system since Chrysler did not do a good job with this. Add a somewhat thick wire from the firewall to the heat shield on top of the intake manifold. You could also add a wire from the negative battery terminal to a radiator support.

 

Running some Seafoam through the system also never hurts.

 

That should give you a start on things...

[86customanche]

Is the fuel rail pressure test only possible with engine running?  Or can it be done while attempting to start?

[HOrnbrod]

Yes, a fuel pressure test can be done while cranking the engine.
 
But first, check for fault codes.   http://comancheclub.com/topic/28111-reading-obdi-91-and-92-mj-fault-codes/
 

 

I would also add a few ground wires to upgrade the system since Chrysler did not do a good job with this.

 
Huh? I think you are mixing up Chrysler and Renix.

[1989 Eliminator]

Yes, a fuel pressure test can be done while cranking the engine.

 

But first, check for fault codes.   http://comancheclub.com/topic/28111-reading-obdi-91-and-92-mj-fault-codes/

 

 

I would also add a few ground wires to upgrade the system since Chrysler did not do a good job with this.

 

Huh? I think you are mixing up Chrysler and Renix.

 

Yes you are right... I got carried away! :doh:

 

But, making sure the grounds are clean with good contacts are always a good thing to do.

[86customanche]

Does the fuel pressure test need to be done with a special tool or can any pressure guage work (knowing it might get fuel in it and be damaged)?

 

 

Got these codes:

12                                  <<< new battery installed months ago.
Battery disconnected.
13                                  <<< this appeared after I disconnected MAP vacuum hose while engine running, causing it to stall.
MAP Sensor.
33
Air conditioning clutch relay.
35
Cooling fan relay.
36
Air switch solenoid circuit.

[HOrnbrod]

You have codes that are not supposed to be there. Try a hard reset on the ECU as follows. Might just work............

 

1. Disconnect the POSITIVE battery Terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.
2. Reconnect the Battery Cable
3. Turn Ignition Switch to the "ON" position but DO NOT start the engine
4. Turn Headlight "ON"
5. Turn Headlights "OFF"
6. Turn Ignition Key "OFF"

The PCM Adaptive memory has now been flashed, or erased from the PCM.

 

EDIT:  For the fuel pressure pressure test you can rent a gauge set from AZ of one of the other parts store chains that have the correct fittings for the fuel rail. It's free.

[HOrnbrod]

But, making sure the grounds are clean with good contacts are always a good thing to do.

This is very true.

[86customanche]

I cleared the codes yet the only code now not shown is the "13 MAP".

I checked and cleaned most grounds, although I couldn't remove the firewall bolt. It felt like the firewall was going to bend before the bolt would turn.

I was able to start it after a lengthy cranking session, and it idled nicely for a few minutes. I was able to rev up to 2500 briefly then it stalled and couldn't be started again.

When turning the key to check the codes I can hear a brief hum behind and below, fuel pump?

I've got some Seafoam, where does it go?

More later......

[HOrnbrod]

You shouldn't have a code 13 if you did the hard ECU reset correctly, unless your MAP sensor is bad or it isn't receiving it's 5VDC reference voltage. Pull the 3-pin connector off the MAP sensor, turn IGN ON, and check for voltage across pins C (+) and pin A (GND). This is the MAP's reference voltage and it should be very close to 5V. If no voltage is present, verify pin A reads continuity to GND. If it does, replace the MAP sensor.

 

And yes, the hum you hear is the fuel pump.

[1989 Eliminator]

I cleared the codes yet the only code now not shown is the "13 MAP".

I checked and cleaned most grounds, although I couldn't remove the firewall bolt. It felt like the firewall was going to bend before the bolt would turn.

I was able to start it after a lengthy cranking session, and it idled nicely for a few minutes. I was able to rev up to 2500 briefly then it stalled and couldn't be started again.

When turning the key to check the codes I can hear a brief hum behind and below, fuel pump?

I've got some Seafoam, where does it go?

More later......

 

Seafoam just goes in the gas.

[91Pioneer]

Seafoam just goes in the gas.

Incorrect.

[1989 Eliminator]

 

Seafoam just goes in the gas.

Incorrect.

How so?

You can also put some in the intake manifold through a vacuum hose but I do not think that is needed for his case.

[86customanche]

I'm still trying to start the engine and figure this out.

After a lengthy cranking, I immediately checked the fuel rail valve and there was no pressure. (I've yet to get a gauge to check the actual value). I do hear a brief pump sound when turning the key on.

I swapped fuel pump relay with another, seems to be ok.

I removed the fuel regulator and reinstalled, how is it checked? Is the fuel regulator the last picture?

I found the fuel filter and it appears old? See picture.

Then I noticed a hose hanging down, which comes from the top of the fuel tank. There are numerous metal fuel lines, one appears to have a broken hose piece, is this related to the broken hose hanging from the top of the tank?

 

[HOrnbrod]

Dude:

 

1. Replace fuel filter. It looks the original from 1992.
2. Do a fuel pressure test with the gauges. This will test the regulator and pump.

3. Troubleshoot or replace the MAP sensor as described to get rid of the #13 fault code.

 

You're just running around in circles - it's best to do things logically. The broken hoses are vent lines for the tank and will not cause a no-start condition.

[86customanche]

The 13 Map code went away with the reset. It probably existed when I disconnected the MAP vacuum line last week when I got it started.

I'll do the fuel filter.

[Jackrabbit41]

I had the same problem but it ended up being that my coil wire was touching something else and it was breaking the circut

[86customanche]

I installed a new fuel filter.

I swapped the auto shutdown and starter relays.

I got it started again, idled for a minute or so, then it cut off. Immediately checked fuel valve and very little pressure.

My local Advance doesn't have pressure testers so will try to get to AutoZone.

[1989 Eliminator]

Something is not holding pressure it seems like... the pressure regulator, fuel lines, and fuel pump are fuel system parts that hold/regulate pressure. So any of these components could be the culpurit if leaking.

[86customanche]

So I'll look for a fuel leak, although I haven't smelled any gas. I'm assuming a pressure leak in the fuel system would leak fuel, unless it's the pump which would leak into the tank and not be noticeable.

 

Thanks Comanche Club for the ideas, gladly accepted by this novice mechanic.

 

(standard disclaimer... Dad borrowing son's Comanche Club account, while charged with running the Comanche every few weeks while son is out of state)

[86customanche]

I thought I had it. Replaced the fuel pressure regulator and it started, after a minute I stopped it. Then it wouldn't start.

I disconnected the fuel filter and cranked it, lots of fuel getting pumped on the ground so it seems the pump works well.

I don't see any leaks of fuel.

 

If I prime it, and cut it off, I can hear fuel returning to tank. Others have said "check valve", is that part of the fuel pump?

[86customanche]

I'm fairly certain I've found the problem.

The 3 inch hose from the fuel pump is crumbling, and wasn't tight on the metal fuel line. Clearly this would allow fuel to drain back into the tank and result in very little or no pressure at the rail.

The pump itself seems to run fine, but I'll probably replace the entire unit now that the tank has been removed.

The fuel strainer was loose and rattling around in the bottom of the tank.

 

[86customanche]

Ok, so I've bought a Carter pump, P74155.

Sigh, naturally it doesn't fit the existing hanger assembly.

The rubber mounting rings are crumbling; the new rings don't fit snugly in the assembly.

 

Should I replace the entire assembly and pump? Delphi unit?

 

http://www.autozone.com/fuel-delivery/fuel-tank-sending-unit/delphi-fuel-tank-sending-unit/jeep/comanche-4wd/1992/6-cylinders-s-4-0l-mfi/342630_923754_0/

[HOrnbrod]

The Autozone sender you linked to is for a Cherokee, not a Comanche - won''t fit. The XJ sender is a mirror image of the MJ sender. Can you return the carter pump and exchange it for the Bosch pump? I know they fit.

[86customanche]

Thanks, I'll return the Carter and get a Bosch.

 

BTW, the Autozone link product indicated it would fit the Comanche, not surprised to find another error in my Jeep shopping experience.

 

I find it quite amazing that many many auto parts sites list the Delphi assembly as a direct fit for a 1992 Comanche 4.0.