Need help on 04 RC that won't start

RMBLFSH

RMBLFSH

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Greetings everyone. I've given up and am reaching out to you guys, I've researched all the threads and similar problems. Apologies for the lengthiness.

My 04 RC has run great for the last 5 years, it has 71,000 miles and recently started acting up. Only mods are billy boat long tube headers, high flow cats with cut outs upstream and Hennessey cold air intake.

A month ago I was driving on the freeway and all of the sudden the truck just stopped running while on the freeway going 70 mph, gauges still had power but no rpms. I coasted off and whenever I would try and restart it, it would try and crank but not actually turn. I waited for about 15 minutes and it started again but required some throttle to keep running. Then it ran fine for a day, next day it stumbled a little while on the freeway again but recovered and seemed fine.

Then two weeks ago I was backing out of the garage, truck had been running for about 2 or 3 minutes and then it did the same thing and just stopped running. Still had gauge power and audibles. Would push the start button and nothing happened, no starter, nothing. After disconnecting the battery and reconnecting it and checking grounds it started again. I hooked up the code scanner and it said it couldn't communicate, this was while the truck was operating either engine running or off.

Kept trying and eventually the scanner did connect with the PCM and communicate, only codes it showed were O2 sensors which was expected. Cleared the codes and the truck worked fine for two days then it started doing the same thing, but in decreasing durations. Maybe 15 seconds and then die. I thought it was a ground or battery related and checked all ground points accessible and when it was running the alt was putting out 14V so no issue there. The battery is new and all grounds are clean and tight. I don't think it's a relay issue with the fuel pump or starter, I swapped those with others and still no start.

After reading through similar issues the recommended places to start was TPS, IAC, Crank Sensor and Camshaft sensor. I cleaned the IAC and replaced the TPS yesterday, did the full proper restart unplugging the thee feeds to the PCM, still nothing when I push to start. Gauges light up and sweep, but no crank. Getting out of the truck while the ignition was on all of the sudden the fuel pump started and then shut off. It hadn't been doing it's normal startup upon ignition. So, don't laugh, I rocked the truck and it would intermittently turn on and off. I actually have an audio of it if anyone is interested. I also have videos of the scanner realtime analysis when it was running. So figured it must be fuel pump related, however it doesn't make any sense that the truck won't crank just because the fuel pump may be bad. It has 3/4 tank right now.

Went to recreate the fuel pump issue and now it doesn't do that nor does it crank. It also won't connect to the PCM. So, next step recommendations? Should I bother changing the crank and cam sensors or is the PCM toast? Anyway to test to see if its the PCM?

THANK YOU!!!
 
Thx, I’ll take a look under the fuse box tomorrow. Yes, it always starts immediately and runs great.
 
The trucks are designed with a will to live so most of the sensors you've mentioned, won't cause what you're describing. Many of the systems are tied together in ways you wouldn't expect.
The self-diagnostic systems can't pinpoint specific issues very often. If the electrical system goes haywire because something is grounding out, mixed signals come out of the diagnostics.
Do what you can yourself- looking around at wiring, etc. and do check the underside of the fuse-box.

Be thankful it isn't a new.
My Jeep Grand Cherokee for example, has FIFTY Microprocessors that all talk to one another. Oh Joy!!!!.....
 
Long shot.. look where the wringing loom routes on the back firewall.
Ensure one\some of the connectors have not failed and the loom slouching and touching the header and melting.
 
i would check the wires to the starter. the headers may have melted them.... fix that and it should crank well. Then check the otherside behind the valve cover and make sure the wires are not burned from the headers.... the 06's had the CPU issue more so than the 04's. the 04's are solid!!!! and the brakes don't seize..... best model... :)
 
Thanks for the feedback guys!! So, I checked under the fuse box and all clean and good there, also nothing dangling or melted underneath the chassis.

So I tried the start button and nothing. I figured I'd try the rocking thing with it in gear and with the fuel sloshing in the tank I heard the fuel pump start and stop. I put it in neutral and pushed to start and it cranked right over and started, then stalled. Then tried leaning in the door jamb applying pressure towards the rear of the truck and was able to get the fuel pump to engage without sloshing the tank just by pressure on the cab.

Which makes me think it's a ground at the fuel pump module that is loose? I looked at the wiring diagram and I can't tell if it has an external ground or if it's in the loom. I reached up from below and all wires seem snug, took a pic with my phone and everything seems as it should. Which makes me think it's not the pump but something in the wiring at the module.

If so, next step would be pulling the bed to get to the top of the fuel tank and the fuel pump module unless you all think otherwise?

I have an audio file of it, but can't upload it.

Thoughts?
 
RMBLFSH said:
Thanks for the feedback guys!! So, I checked under the fuse box and all clean and good there, also nothing dangling or melted underneath the chassis.

So I tried the start button and nothing. I figured I'd try the rocking thing with it in gear and with the fuel sloshing in the tank I heard the fuel pump start and stop. I put it in neutral and pushed to start and it cranked right over and started, then stalled. Then tried leaning in the door jamb applying pressure towards the rear of the truck and was able to get the fuel pump to engage without sloshing the tank just by pressure on the cab.

Which makes me think it's a ground at the fuel pump module that is loose? I looked at the wiring diagram and I can't tell if it has an external ground or if it's in the loom. I reached up from below and all wires seem snug, took a pic with my phone and everything seems as it should. Which makes me think it's not the pump but something in the wiring at the module.

If so, next step would be pulling the bed to get to the top of the fuel tank and the fuel pump module unless you all think otherwise?

I have an audio file of it, but can't upload it.

Thoughts?
Click to expand...
Start at the beginning.
From battery to starter solenoid. Solenoid connection is 90% of these problems, look for loose connection,dirty, melted etc. That will give the symptoms you describe, fuel pump on/off no crank, engine stopping. Then go chasing ignition system power supply, then oil pressure sender/wiring, Fuel pressure sender/wiring. Most issues are basic so do the basics first and are the cheapest and easiest to find. They are also the ones that don't show on diagnostics. Most mechanics these days can't diagnose, they just rely on what the computer says. They have lost the ability to do the basics. It used to be power then fuel then timing/air/exhaust I put my money on power or an intermittent break in supply
 
Ok, update. Same issues, I pulled the battery power and ground, as well as terminal at the ipm, removed and reinstalled all the ground connections, removed and reinstalled the starter cables, did the pcm cables touching clear and still no crank and no communication on the scanner with the pcm. I'm getting 12.8v at the starter, but nothing at the lead to the solenoid when starter button is engaged. So, that leads me to believe its the power getting to the solenoid as clearly the starter works.

I defaulted back to the rocking the truck forward and back and heard the fuel pump blip so hopped in and it fired up and then died. Tried to start again and nothing, checked the starter again and same thing 12.8V at the starter but nothing at the lead going to the solenoid with starter button engaged. Got out from under truck, sat in vehicle, turned key and heard fuel pump active, push to start and it fired up and ran for a couple minutes and then died, the scanner did communicate with the computer when it was running and didn't show any codes however it says error communicating whenever it's not running and just in ignition on mode. Then same thing, nothing.

It seems the starter solenoid, fuel pump and ecu are in a closed loop. The no power to the solenoid makes sense why it won't start, but it doesn't explain why it does start and is clearly sending power to the solenoid when the fuel pump is working during ignition cycle. Which takes me back to something faulty with the fuel pump, if it was the ecm or pcm I wouldn't think that the fuel pump would stop and start intermittently while rocking the truck allowing it then to start unless it's a faulty sensor at the fuel pump that the ECU or PCM is looking for and not receiving until I rock the truck and it then sees the closed loop and starts but then can't read it any longer when it's not moving.

Thats the one thing that is consistent, is the only time it starts is when the fuel pump turns on in the ignition sequence when the key is turned.

Thoughts? :)
 
RMBLFSH said:
Ok, update. Same issues, I pulled the battery power and ground, as well as terminal at the ipm, removed and reinstalled all the ground connections, removed and reinstalled the starter cables, did the pcm cables touching clear and still no crank and no communication on the scanner with the pcm. I'm getting 12.8v at the starter, but nothing at the lead to the solenoid when starter button is engaged. So, that leads me to believe its the power getting to the solenoid as clearly the starter works.

I defaulted back to the rocking the truck forward and back and heard the fuel pump blip so hopped in and it fired up and then died. Tried to start again and nothing, checked the starter again and same thing 12.8V at the starter but nothing at the lead going to the solenoid with starter button engaged. Got out from under truck, sat in vehicle, turned key and heard fuel pump active, push to start and it fired up and ran for a couple minutes and then died, the scanner did communicate with the computer when it was running and didn't show any codes however it says error communicating whenever it's not running and just in ignition on mode. Then same thing, nothing.

It seems the starter solenoid, fuel pump and ecu are in a closed loop. The no power to the solenoid makes sense why it won't start, but it doesn't explain why it does start and is clearly sending power to the solenoid when the fuel pump is working during ignition cycle. Which takes me back to something faulty with the fuel pump, if it was the ecm or pcm I wouldn't think that the fuel pump would stop and start intermittently while rocking the truck allowing it then to start unless it's a faulty sensor at the fuel pump that the ECU or PCM is looking for and not receiving until I rock the truck and it then sees the closed loop and starts but then can't read it any longer when it's not moving.

Thats the one thing that is consistent, is the only time it starts is when the fuel pump turns on in the ignition sequence when the key is turned.

Thoughts? :)
Click to expand...
You need to follow the steps. You have power to starter that's a start. Next step where does it go to from there? It is definitely a power supply disruption. Forget about ecus or fuel pump. those are results of no power. Trace your power from starter and follow the steps. It maybe the ignition switch, but follow the power cable you will find the fault. Don't just replace parts, you need to test and find the real reason for the intermittent power supply
 
So, I unplugged the immobilizer while on working on the ignition and it starts perfect now every time. Yes it's dies after a 2 or 3 seconds since it's unplugged, however fuel pump immediately kicks on and starter every time. Looks like I found the culprit. Thank you for the support and info! I'll let you know once I replace it if all is good.
 
RMBLFSH said:
So, I unplugged the immobilizer while on working on the ignition and it starts perfect now every time. Yes it's dies after a 2 or 3 seconds since it's unplugged, however fuel pump immediately kicks on and starter every time. Looks like I found the culprit. Thank you for the support and info! I'll let you know once I replace it if all is good.
Click to expand...
Yeehaa we have a winner!
So glad. It just does your head in having electrical gremlins. I remember 40 years ago it was rev counters that gave us a lot of grief. Unplug them and that was that. Being a young fella it wasn't anywhere near as fast without a rev counter lol
 
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