BigBlue

[quote author=MCummings link=board=7;threadid=18903;start=0#msg177458 date=1062027194]

1. Try some JB weld

2. Uhh, ??? What? How does air make pressure? IF anything it should compress, and appear as less pressure.

3. That's odd

4. You mean a PCM. The LP relay is integral to the PCM, only rated for about 1.5 Amps

5. To high of a load,, accidently shorted out, or, just felt like not working anymore.

Hope this helps.

Merrick Cummings Jr
[/quote]

1. I'll try that.

2. It didn't make sense to me either but I just thought I'd throw that in there.

3. I know it's odd.

4. In the underhood fuse box, there's a relay in there called a fuel pump relay. I don't think the PCM itself was hurt cause the rest of the truck works great.

5. I still don't know how the relay blew. Maybe it was cause I didn't ground the grounding bar seperately. Do you know of a better way to hook up the trigger wire instead of the positive wire in the stock lift pump harness (the wire I used from that was yellow).

OlBlue

OK, factory wired. Remove the ground wire and the relay mounting bracket from the firewall. With the red wire powered (not the yellow) touch the mounting bracket and ground to a grounded place to see if you hear the contacts open and close. If so, the factory got red and yellow reversed. Yellow would be the power side of the contact and red would be the trigger wire.

Even with (2) 40amp relays, pulling a few milliamps each, you shouldn't have blown a fuse or the factory relay.

BigBlue

I'll try that and let you know what happens. Your basically saying to touch the yellow wire to the other wire in the lift pump harness and then grounding it all through a common ground, right? As you can probably tell, I'm not the best when it comes to understanding wiring so please bear with me. I think the yellow wire might be the right wire though cause every time I'd bump the starter to prime the system (before it quit working), the pump would cycle like it's supposed to. Now it won't even do that. It's not getting any power through that wire.

BigBlue

The trigger wire does nothing more than turn on the relays, right? Kind of like a remote wire for an amp on a stereo system. All it is is an ignition on switch that only gets power when the key is in the on position. If that's the case, couldn't I just find a wire that is an ignition on only and splice into that and use that as the trigger wire? Why do I have to use the lift pump wires?

OlBlue

This is just a test to see if the red wire powers the relay - makes the relay operate - instead of providing power to the load. Yes, like the trigger wire on the stereo amplifier. The trigger wire isn't supposed to provide power to the load, just turn the relay on when powered. Leave the yellow wire dead. If you power both at the same time, you won't be able to tell (by listening to the relay "click" closed) if the red wire is responsible. Instead of taking the relay off the firewall, if it's wired with the disconnect shown, operate that disconnect with the yellow wire dead. Any means of powering the red wire and unpowering the red wire while listening to the relay will tell you if the red wire is the trigger wire instead of the yellow wire.

I aplogize for this getting so long winded, and maybe I shouldn't have jumped in with both feet, but there must be a reason the OEM source is now dead, and the only thing I could think of was an overload caused by running the pump instead of activating the relays.

In the wiring diagram, the manufacturer actually shows a switch for the trigger wire instead of using the OEM pump wire. If you remember to turn it on, that would work just fine. I would most likely forget.

If the red wire makes the relay click with the yellow wire dead, then the wiring diagram is a misprint or the relays were wired wrong. If the yellow wire makes the relay click with the red wire dead, then......I will have wasted a lot of your time >

OlBlue

OH, forgot this! The OEM pump has it's output intentionally reduced during starting. If you power the pusher pump while starting, it could push the fuel pressure too high and make your rig hard to start. So, if you choose to find a source in the fuse panel to trigger your relays, you might look at finding one that is on when the key is in the on position, but not on when the key is in the start position.

BigBlue

That's why I only see 18 psi while cranking (if I even see that, usually it's about 8). If the pump isn't on in the start position, then wouldn't that not supply fuel to the injection pump and cause air to get in the lines? Whenever the fuel pump isn't running, I'm not getting any pressure. But it would be alright to use just an ignition on wire to power the pump?

AlpineRAM

bb: While cranking the PCM does duty cycle the LP. Basically on-off-on-off etc.
I'd do the following- measure with a 12V light between the yellow/white cable of the stock LP harness and ground. If it lights up when the pump is supposed to turn ( like after ign. on for some seconds) you have the trigger wire.-If not test black/white to ground.
If there is nothing in any case you know you have killed the ECM output. Then you could try to do the following. Use a wire that's on engine run to drive the relays, and add another wire connecting to a that connects to a wire that's hot with ignition on, through a pushbutton to drive the relay for prefeeding. With that you can do your own duty cycle for startup.

Your q about air entering when the lp isnt running: As long as the system is tigh the VP44 can suck some fuel- no air should enter through the lines anyway.

HTH

AlpineRAM

ps wire colors stated as in 99 service manual

BigBlue

How important is it for the LP to cycle while cranking?

What about the pressure issue? I need to get the pressure's down. But how do you compress a spring? Should I maybe cut half a coil off at a time and see how that works? I'm going to order a new pressure spring today so that would only be a temporary fix.

BigBlue

I called Product Engineering and told them the problem I was having with the pressures on the pump. At first he couldn't believe that I was seeing that much pressure. The most the've ever gotten out of it was 25. Anyways, he told me to go and cut one coil at a time out of the spring and try it. Cut the first coil, it held 18 for about 1 minute and then gradually worked itself up to 30+. Cut another coil, I'm holding 13 at idle and 12.6 at WOT. ;D Granted, this is just free revving and no load, but I'm happy I finally got that problem taken care of. All that's left now is hooking up that trigger wire and fixing the leak.

By the way. Mike (the guy I spoke to at PE), told me that they are asking anyone with a 4200 pump on their vehicle to return it to them. They made some major changes to it and they will replace the old pump with a new one and ship it back to you for free. So any of yall with a PE4200 might want to give them a call and ask them about it. As soon as I can part with my truck for a few days, I'm going to send it to them.