hard start/fuel pump relay

[armydisco]

Ok, I backed pinned the fuel pump relay and the power to the fuel pump yesterday. In posit 2 the pump and relay show 13vdc and then goes back to 0, that's the initial surge of the pump before it starts, ie normal. Then in posit 3, crank, the voltage climbs and hits 12-13vdc and voila the engine starts. I left my meter on while running the truck to make sure I kept voltage coming out of the relay to the fuel pump. All good no prob, then once it decides not to start no volt out of relay, sounds like a bad real not closing or something, so I swap with known good relay and same prob. No volt out of fuel relay = no volt to pump. Let it sit and voila voltage coming out again, starts fine.
The charging and starting schematic shows a wire from the ECM to the fuel pump relay. Does anyone know what it's doing? Could the ECM be bad and sending the wrong signal, and not allowing the relay to close like it should? The wiring seems to be all good, I double checked it yesterday and found no problems.

( i do have relays on order for back up)

[dismalrobot]

If you look in the Disco II forum under "Engine start casuses?", you'll see the starting issue that I am having and what I have done so far. Wondering if it could be a faulty fuel cut-off switch. I am not sure if you are having the same symptoms though.

[Rovin4life]

ok, need some info describe in detail your hard start?

before you go fishing around we do have problems with the crank signal.

no signal no fuel pressure.


i want to help you i just need info.

[armydisco]

HARD START- will crank but not start. Then it starts fine and runs no prob.
It looks like it could be a crank position sensor or a cam position sensor. I am in work now on tracing the wiring out to both and making sure nothing is broken or damaged.

[Rovin4life]

check the wiring to the ecu, I have seen it go bad, wiggle the wire and it will stop running after starting.

[armydisco]

The question is where is it bad at??? I have wiggled the bundle from the ECU running up to the center firewall while it is running to see if it would die. I can never seem to pinpoint an exact area. It definitely seems like a wire or sensor. I would love to find a bad wire.

[Rovin4life]

if that doesnt work then most likely its the sensor. had a few those go bad.

[armydisco]

Got OBD II reader comin so I'll be able to isolate it better and breakdown/clear my SES light. Closest dealer is 3+hrs and I really don't now anyone worth takin it to around here. (lower Alabama)
I am going to try and get all the insulation replaced on the wire bundles today. Most are cracked and dried out from heat. While I am doing that hopefully I'll be able to inspect the wiring.
Thanks for the help, I'll let you know what I find.

[armydisco]

Okay hooked up a reader and got a P0473 gear 4 code. Cleared code, SES light came right back but reader not showing anything.
Anybody got any ideas I am about to drive it out to the range and have some fun.

Of course it won't start!!

[armydisco]

Uhh forgot to tell you guys I am dyslexic, code P0734 Gear 4 Incorrect ratio. Only code it picks up. Had the battery disc for a while, maybe ECU lost memory.

Probabaly doesn't help but it's the right one.

Thanks for any and all help.
Rob

[armydisco]

This is pretty cool talking to my myself.........Update # ?? Anyway talked to a lot of diff people and did some reading, got a crankshaft position sensor on order. As per the repair manual difficult starting and no code is related to the CKS going bad/failing. Has anyone replaced one? The book shows an adjustment from the "Test Book" after install. Is this just to reset the light??? I don't see what else you could do unless you messed up the spacers or something.

Thanks for all the help, if it wasn't for the forum I would have shot this thing, at least if I don't get an answer on my problem I can read about everyone elses problems. Misery loves company.

[Rovin4life]

you have a maf sensor code that is relative towards the tranny but dont worry about it.

just put in the new sensor and away you go.

[armydisco]

Thanks Rovin4life, it should be in soon so I'll post the results. Hopefully everything will be back to normal.

[armydisco]

Ok, got it running again. Changed out the crankshaft position sensor and it started right up with no prob.
It seems to run good, but at a stop in D it wants to go, seems a lil jumpy/idles funny. In park it goes away and driving seems good.
Guess that's the next prob to fix, at least it is starting!!!