Died, now stumbles on restart attempt, no sustained run

[llhat]

Long.

Background

1989 Comanche 4.0 renix automatic 169k

 

This morning, added oil, and while hood open unplugged and reconnected the square connector on the TPS, ( had been having to shift transmission manually).. just an attempt for this.

 

Cranked, started,  drove to take off trash about 4 miles away, not turning it off...  On return home,

less than 1/2 mile from driveway...  no engine power,  slid to neutral and attempted restart, nada

coasted to driveway, down driveway and to outside my shop (at least i did not have to push it).

 

once stopped again, attempted restart.

will 'catch' and fire about three or four cylinders, but will not sustain run condition.

Tried thus far:

unplug and re-connect:

1.Both TPS connections

2.checked coil high tension connection to distributor

3.  CPS connection

 

then tried start again, no change.  I can hear fuel pump cycle.

I then unplugged MAP sensor,  seems a spacer in the connection on the MAP side fell out.

attempted retrieval, but too hot in that area.  I reconnected the MAP connector, seemed "OK"

 

Still no change,  start, hits, stumbles, but no sustained run.

 

Gave up for now.. too damn hot.

Next..  plan of action...

 

1. verify fuel pressure

2.  test CPS output

 

What else???

Thanks in advance.

 

 

[eaglescout526]

Have you inspected the NSS internals since owning the MJ?

[Torq_Shep]

I have had this problem with a bad ballast resistor. Although you will likely see that when you check fuel pressure.

[llhat]

i can only pray it is that simple !!

 

will be a couple of days before i can reexamine.

thanks for the responses thus far.

 

[Htchevyii]

I highly recommend Nick's REM. It makes diagnosing or even realizing that you have an issue so much easier.

 

A few weeks ago while on a 1000 mile trip in the '89 XJ, the fuel pump relay failed. I couldn't remember which relay was which, (they are now labeled), so I switched them all around. The Jeep immediately fired up, but now I have a code for the o2 heater on the REM. I had swapped the bad FP relay with the o2 heater relay. If not for the REM, I would have never known this and just driven around in open loop for who knows how long.

 

 

https://nickintimedesign.com/product/renix-engine-monitor-ii/

 

 

 

[gogmorgo]

Easy test for bad ballast resistor, just bypass it, connect the wires on either end together. If that fixes it you’re laughing. Finding a new one or leaving it permanently bypassed is up to you.

 

NSS going out prevents cranking, shouldn’t kill the engine or make it run rough. 

I might add the TPS to the sensor testing list. Cruiser had a tip for adjusting it too. Also some tips for the trans shifting issue.

 

If it’s not fuel related I’d be looking at ignition components. If you don’t know how old the distributor cap and rotor are it might be wise to change them. 

[llhat]

"finally" had a chance for more diaganostics

don't sound too good...

 

I started with 'jumping' the ballast resistor,  but went from terminal to terminal with wires still attached.

still same situation as described in OP.

I then retrieved my fuel pressure gage, attaching to the schrader valve on the fuel rail.

 

Hit the switch... uh oh  no pressure.

checked to ensure i had gage fully connected, it was.

 

when starting i will burble and hit a cylinders and die.

IF i hold down the switch to starting position, it will burble .... and die.

I CAN hear the pump cycle for a few seconds

 

next i made a jumper for the ballast resistor removing the ceramic from the equation completely

the pump 'seemed' a bit louder, but no fuel  pressure showing on gage...

 

IF i try starting repeatedly, I can see gage flutter just a bit and if i cycle switch a few times it will burble longer.

if i hold switch on start, it will fire but never get rpm increase to even an idle

 

so in effect  no fuel (and i know i takes 39psi to run. to rule out gage, I removed and then depressed schrader valve manually.. nuttin

 

so..  i guess start with filter...   see if i get flow on output end,  then input end.

I have replaced this pump and filter,  will need to look back how long ago.

 

wonder about regulator,  could be defective?  no vacuum = higher pressure

its only been hundred or so miles since fill up so pretty certain not out of gas in tank... 23 gallon

I know gage is off, but even then I have run gage down even further than it is now without running out and

it only took ~17 gallons to fill.

 

not looking forward to pulling that pump, but seems that is the direction unless i missed something..

 

[Ωhm]

KEY OFF. On the Starter Relay, remove Fuel Pump Ballast Resistor wire. Using the Battery Terminal at the Starter Relay, jumper Battery Terminal to the removed Fuel Pump Ballast Resistor wire. Fuel Pump should go ON. Attempt to START vehicle. Any luck.

 

 

[gogmorgo]

Pull a line off the outlet of the filter, see if you’ve got fuel flowing there. If you don’t, pull the inlet line off to see if you’ve got flow there, indicating the filter is blocked. 
But I bet the issue is in the tank. If you didn’t change the rubber line from the sending unit to the pump, or if you did but didn’t use submersible fuel hose, I’d be willing to bet that failed. I also had a not-great-fitting aftermarket pump come out of the sending unit in a way that it wasn’t pulling fuel from the bottom of the tank, so I’d essentially run out of gas with roughly 1/3 tank remaining. 
 

 

[llhat]

thanks to Ohm and gogmorgo ...

 

appreciate the method to direct wire the pump easily... great test.

I did try the jumper on the start relay,  connecting removed wire to + battery  pump does run, even with the wires to ballast resistor completely disconnected and those two wires NOT jumpered

 

I let pump run in jumpered state and 'still' no pressure showing on gage connected to schrader valve on fuel rail... even after a minute.

so i'd guess that would disprove anything with any of the relays under hood...

 

guess now it is time for lying on ground and checking @ fuel filter,  inlet and outlet.

 

looked back in records, dang been a long time since pump replaced,  but only about 60 miles since i filled up with 14 gallons of fuel, so gogmorgo may be on to something amiss in the tank    just NOT wanting to go there...  I had put a new tank in years ago...

 

now wondering IF i have to drop the tank, as I remember it was a tight fit for access to the pump bung on the tank...

[TurboedMJ]

It isn't too complicated to drop the tank. It's a lot easier to drop the tank and check the fuel pump than to check the fuel pump with the tank still in the truck. I did the first method twice in the time it would've taken me to do it the second way. 

[ghetdjc320]

Fuel pump or connection in tak

[llhat]

well to update...

I had it towed and hired it out... just did not want to lay on ground/grass/ gravel and I

could not get it in my shop by myself without it running.

 

Just got it back yesterday 

reported to me first pump was defective out of box, but second a charm

believe this shop sources from Car Quest....

 

then starter failure  ...  crap... told them to fix it...  drove it home from shop.

 

next...  new battery cables,  and figure out the aw4 transmission issue...  (must manual shift)

 

 

[Eagle_SX4]

Not a big surprise on the fuel pump. Those rotary vane pumps are hit or miss. I replaced 2 in my Eagle before I switched to the newer turbine style.