Excessive cranking/stumbling- many new parts

[jackmb]

92 4.0L, m/t, ~115,000 miles. New to me.

Last week I replaced the CPS, TPS and fuel pump. Two days ago I cleaned the throttle body and today I replaced the fuel filter, cap, rotor and plugs. The battery has ~12.5 volts.

The motor will crank for an excessive period (7-ish seconds) before starting, and when it does it really stumbles quite a bit. After a bit it will smooth out, but still acts weird, stumbling and almost (sometimes fully) dying when pressing the throttle.
A video is worth a thousand words.... Any ideas what now?

http://www.youtube.com/watch?v=fdETFYiLz7w

 

[my2monkeys]

Hmm, heard the video.

Did you disconnect the batt after all the new parts for the comp. to relearn?

Check all the grounds and MAP vacuum and o2 wires.

Clogged exhaust?

 

[jackmb]

I had the battery disco'd when I changed all the parts.

The MAP vacuum is good, I checked it by disconnecting it and the idle changed.
The rubber vacuum isn't in the best shape on the fuel pressure regulator, but it doesn't appear to be leaking. I am going to replace the rubber ends of the vacuum lines, but I need to bring them with me to the store to get the correct sizes.

The battery cables aren't in the best shape, but I don't believe that is the problem. I will be replacing them with a set I'll be making of 2ga cable with terminals ordered from 5-90 as soon as they arrive anyway.

The excessive cranking could be a bad cable/ground problem, but once it's running, that shouldn't be a factor. It seems more like a weak spark? Or too rich? Or too lean? :dunno:

 

[my2monkeys]

Try unplugging the o2 sensor and see if it starts and revs any better.

 

[jackmb]

Tried it with the o2 sensor unplugged- no change. 7+ sec of cranking to start and it stumbled immediately and died after about two seconds.

I'm going to pick up some vacuum line and try that next...

 

[Ecomike]

Check the fuel pressure with a gauge, the fuel pump ballast resistor (bypass it to test) and the vacuum line to the fuel pressure regulator for leaking fuel into the vacuum line.

Are the plug wires also new?

What spark plugs did you use?

Check for pair of crisscrossed plug wires, on the wrong cylinders. And check the Distributor index at TDC on piston #1

 

[SBpunk]

Fuel injector or fuel pressure will do this too. I'm having a similar problem but I know its because I put a new fuel pressure regulator and injectors in.

 

[Dragonslayer]

Get an ohmmeter and a Mityvac tool and test the MAP sensor electronically.

This website (below) describes the procedure better than the FSM:

http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-map-sensor-1

This hit the nail on the head and saved my bacon a while ago.

 

[joe_peters]

Use a fuel pressure gauge and test the pressure leakdown time.

If it is too quick try the test with the return line pinched--engine OFF.

If it still drops too soon put a one-way check valve in the supply line between the external filter and the tank.

 

[jackmb]

It appears to be a fuel pressure problem....

- The vacuum lines are def good now- the elbow for the fuel pressure regulator was dry rotted (but not leaking) but I replaced that elbow and one more last night anyway.
- Plug wires are not original, but not brand new. Previous owner changed them at an unknown time.
- The new plugs are Champion
- I jumped the ballast to test, no change.

Then I put a mechanical gauge on the schrader valve on the fuel rail, it would only go up to ~16psi when cranking/stumbling/immediately stalling.

With the ignition off, I jumped the fuel pump relay and watched the gauge; again, only 16psi. It would take about 2-3 seconds to get up to 16psi as well.
video - http://www.youtube.com/watch?v=wFslGGf3kmk

The fuel pump and filter are brand new. As in, 50 meters driven on the pump and 0 on the filter.

Is this a bad pump? It was enough of a PITA to change once, but I'd rather return it under warranty and do it again instead of drop $60+ on a FPR. Or is there another cause?

 

[joe_peters]

Check the flow direction of the fuel filter you installed.

 

[jackmb]

The filter is installed correctly.
I removed the Fuel Pressure Regulator to test-swap it with a friends- the screen on the fuel side of it was intact, but there was some rubber bits (from the diapragm?) on the outside. Which is weird because the screen was intact. My friends FPR leaked so I ordered a new one a few days ago from RockAuto.com. Waiting on it to arrive...

 

[jackmb]

Still nothing.

But, now I'm thinking I have a bad pump (yes it's new, but check this out...)

New parts:
Fuel pump
Fuel filter
Fuel pressure regulator
Injectors
Crank Position Sensor
Throttle Position Sensor
Cap
Rotor
Plugs

I've pulled the fuel line where it goes into the filter and turned the key for it to prime. The pump primes for about a second (same duration as always).
Same results when testing at the filter outlet.

I removed the fuel supply line at the rail and primed it, no fuel comes out.

When it cranks, it takes a while, but will fire up if I press the gas pedal, and I now have ZERO psi when primed, cranking, and "running". It will not "run" this way for long before bogging down and stalling.

Also, when I jump the fuel pump relay I get nothing. It used to pump when jumped (like I did in the video linked in post #10). But it primes (for a second) when I use the key. Weird.

Bad pump? I'm going crazy (and broke) with this.