Fuel pressure issue. no start

Brumbles88 · **Posted:** Wed Nov 18, 2015 5:22 pm

So I'm back again.

Back story. Finished a rocker job, timing back together everything seems to check out. Go to start, and it just won't fire. Using torque on my phone fuel pressure sits at 30 or 64 psi even when cranking. If I crank it longer then 5secs it creeps to 350 psi but drops once I stop.

Last week I had a service guy out and he found basic the same info. He suggested replacing the fuel filter head as I had an old one. And it could be the possible cause of air in fuel.

So with that replaced, I am still in the same spot. Read a recent post about the pressure regulator and sensor. Seems like my sensor is working fine.when unplugged I get a 26000psi out put and a code. I hear the solinoid buzz when the key is in and it stop when disconnected.

Any ideas on how to verify it's good? Or what else might be wrong?

I can't wait to have it back on the road.

papaindigo · **Posted:** Wed Nov 18, 2015 5:42 pm

You may have swapped the #4 injector electric plug with one of the fuel rail sensor plugs that's identical. I forget which one but if they are swapped no fuel rail pressure and no injector signal = no fire. Try switching plugs unless the plug to injector #4 is physically marked #4.

Mountainman · **Posted:** Wed Nov 18, 2015 8:19 pm

have you cracked open a line to purge air yet? You can drain a battery trying to start these as the air takes a while to get out without a lift pump. Crack one of the lines on the fuel rail, and when it sprays a little fuel (cover with a rag as it's dangerous and can Kill you) close it, and then it usually starts pretty quickly. You'll want a charger on the battery most likely. Especially since the ECU won't let the engine start if you're below a certain voltage, but the starter will still work, which also may be your problem.

Or it's what Papaindigo said.

Brumbles88 · **Posted:** Sun Nov 22, 2015 2:07 pm

So bleed the lines got fuel at all four conetors working front to back. Tried switching the #4 injector and the fuel pressure regulator. But still no start. I'm still only seeing max 300 psi in the rail.

With the regulator connector switched I hear the injector pullsing, and when it's attached to the requestor the a a faint hum. Could this hum indicate the regulator failed open?

Is there a way to use torque to view fuel pump demand or by pass, or when the solinoid is opening and closing?

I'm stumped a :banghead:

flash7210 · **Posted:** Sun Nov 22, 2015 2:29 pm

Is check engine light on? Any codes?
Is there a red dot lit on the instrument cluster?

olypopper · **Posted:** Sun Nov 22, 2015 6:23 pm

Disconnect the FCA (aka mprop, fuel quantity solenoid, etc) on the back of the injection pump and see what your rail pressure does when cranking. It should spike.

Brumbles88 · **Posted:** Sun Nov 22, 2015 7:11 pm

So in the last round of wrenching, I tried unplugging the mprop and didn't see any real change from prior testing. No spike.Assuming this means it's failed open?

Currently have 3 codes ones the transition code, ones for the fcv which is out since I installed a weeks elbow and the 3rd is ambient air temp high.

Very much apperiacate everyone's help.

flash7210 · **Posted:** Sun Nov 22, 2015 7:20 pm

I dont think its the mprop.
Try disconneting the fuel rail pressure sensor on the side of the fuel rail.
With the rail pressure solenoid unpluged, torque pro should display a rail pressure of 26,000 psi.

Its also possible that you have air trapped in the fuel rail.
Crack open the #1 injector fuel line, then crank the motor. This should allow any trapped air to come out.

rankom · **Posted:** Sun Nov 22, 2015 7:35 pm

just a thought , can you go back and check map sensor because it controls fuelling?

olypopper · **Posted:** Sun Nov 22, 2015 11:53 pm

rankom wrote:

just a thought , can you go back and check map sensor because it controls fuelling?

Map controls fueling after startup. His engine isn't building rail pressure sufficiently and that is performed by the CP3 and pressure regulating components on the rail.

Unfortunately, at this point you need to double check everything you just did in the rocker repair.

rankom · **Posted:** Mon Nov 23, 2015 8:12 am

sorry , MPROP check pins , loose connections ??

papaindigo · **Posted:** Mon Nov 23, 2015 9:46 am

You might check out viewtopic.php?f=5&t=59446

IIRC there are 2 sensors on the fuel rail - fuel rail pressure sensor (assuming it's the sensor on the side of the fuel rail) 515963AA or Bosch 0281002534 or maybe a more recent Bosch #0281002921 and fuel rail or fuel pressure solenoid/valve (assuming it's the one on the end of the fuel rail) 5159964AA or Bosch 0281002705. If the pressure sensor or it's wiring are bad then an improper signal is going to the ECU, I think, and hence to the CPP3 so pressure won't build. If the valve is bad, IIRC it involves a spring and it's not unknown for one to stick open, or its wiring then it can stay open in which case fuel is dumped from the rail back to the fuel tank and pressure never builds. When I suggested a switch plug I think it involves the valve and #4 injector. Unfortunately I have no clue how to electronically test either sensor or their wiring beyond a basic wiring continuity check assuming you can find the pins at both ends of each side of the circuit(s)

Brumbles88 · **Posted:** Mon Nov 23, 2015 11:43 pm

Question on bleeding the rail: HOW FAR DO I "CRACK" THE FITTING? Do I tighten it while cranking or just after? I've tried bleeding the rail several times and am just wondering if maybe I'm doing it wrong.

Next in checking the pressure control valve at the back of the rail: If I let it drain into a cup rather than return to the tank I need to plug the port in the fuel line cluster, correct?

Thanks again.

a. waterfield · **Joined:** Fri Oct 02, 2015 5:00 pm **Posts:** 58

You should hear the mprop shut/open in key on condition when removing connector

I have never cracked injector pipes to remove an air lock common rails bleed air quick enough

Disconnect the pipe to the fuel rail from pump at the rail end - crank and observe fuel flow, with mprop disconnects it should be a reasonable amounta. When my mprop was faulty it had no code cel but did create pressure with mprop disconnected. If no fuel flows I imaginen that either Te mprop is stuck open or he key way to the Lp side of the pump is damaged which seems to be a common high mileage failure of cp3 pumps, on Cummins diesels at least...

flash7210 · **Posted:** Tue Nov 24, 2015 7:31 am

Brumbles88 wrote:

Question on bleeding the rail: HOW FAR DO I "CRACK" THE FITTING? Do I tighten it while cranking or just after? I've tried bleeding the rail several times and am just wondering if maybe I'm doing it wrong.

Next in checking the pressure control valve at the back of the rail: If I let it drain into a cup rather than return to the tank I need to plug the port in the fuel line cluster, correct?

Thanks again.

Is fuel dripping out of the loosened fuel line?
If so, you are doing it right. This is just to make sure no air is trapped in the rail.

Yes, you will need to plug the open port on the fuel return block.
Otherwise you spill a lot of fuel on the floor.

olypopper · **Posted:** Tue Nov 24, 2015 8:01 am

Just as an example, I fired my jeep for the first time Sunday after complete tear down and reassembly. The priming procedure went like this:

Primed filter head with button and bleeder valve 4 times until all air expelled.
Cracked fitting at forward end of fuel rail.
Had wife crank until fuel was noted at connection.
Tightened rail fitting and cranked for approx 10'seconds.
Allowed starter to cool for thirty seconds and cranked again and at this time the engine fired immediately.

This is how fast these engines should start when your fuel delivery system is in good shape.

I still think you may have a leak in the delivery system prior to the engine.

rankom · **Posted:** Tue Nov 24, 2015 8:05 pm

ok i think you need to go back to check all sensor connectors ,injector harness plugs what ever was unplugged prior rocker job. next remove rubber fuel line (inlet) to cp3 pump and push primer pump several times if you don't have electric LP, if you have lots of fuel there? then next test is , check fuel return flow and injector return to see where you loosing pressure , also possibility .. mechanical problem (no codes) like Waterfield explained , Lo pressure pump not drawing fuel to cp3 or m,prop mechanical problem like he's jeep had no cel , so take time and start working on this test one at time ,but it is puzzled because everting was ok prior rocker job?

Brumbles88 · **Posted:** Tue Nov 24, 2015 9:47 pm

So plan for the weekend,

1. Install clear lines at intake and outlet of fuel filter.
2. Check to verify plenty of fuel comes out the outlet of filter
3. Reprime and bleed fuels system
4. Verify mprop is working while key is in.
5. Check fuel pressure valve at back of rail.
6. Check recheck all connectors.

Hopefully some thing works out.

When I took it to the shop when rockers failed it ran with a loud tink. Shop took it apart and did a compression test via the glow plugs. They said all cylinders had compression in spec but they couldn't work on it any further. That's when I had it towed back to my garage.

Brumbles88 · **Posted:** Sat Jan 23, 2016 6:34 pm

Finally made time to get back into this.

I added clear lines at the filter. Everything looks clear before the filter but there's a bubble that hangs out in the metal elbow before the fuel line. When I prime it the bubble shrinks till you can't see it but when I crank it comes back into view but u can see fuel flowing past it.
Bleed the rail and still nothing over 300psi.

Next I checked to see if fuel was coming out the back of the rail. Notta. But I got a nice surge out of the return line. This suggested to me the mprop is stuck open. I pulled it out :furious:

.

How much pressure should it take to move? Any simple test to verify function?

pjigar · **Posted:** Sat Jan 23, 2016 9:59 pm

For whatever it is worth: After my rocker job (no in-tank lift pump at that point), all I did was prime the fuel head to purge all air and then cranked twice for about 15-30 seconds each. My jeep fired right up after that.

So based on all the discussion so far, if the jeep worked before rocker job and if it does not fire now then I would only suspect missing/loose connections.

By the way, low ambient air temp code means you forgot to connect a big connector near the headlight under the fender.

Fuel pressure issue. no start

Who is online