D Jet issues continue, Wire routing questions Options

[robkammer]

All: The intermittent fuel pump issue still lingers on our BB. Can anyone tell me where the wire (or wires) that feed pins 12 and 14 on the 14 pin connector are routed from the battery? It's obvious that it goes into, and returns from the hole in the firewall. But does it go all the way to the dash, or just under the passenger seat?

And the color, is it red/white or red/yellow?

This seems to be the cause of the problem. And check out my OBD 914 version below. Only way I could figure how to determine what was failing.
Rob

[robkammer]

Thanks for the print. I thought I had it solved as well. Headed out for a 10 mile ride but turned around when I realized I had left my phone behind. Car died three times on the way back but restarted each time.

My home made OBD confirms the fuel pump circuit is the issue. during more testing we discovered that pin 14 and 12 do not always have 12V. And when they do we can't wiggle, jiggle, or bump anything to recreate the disconnect.

We were at Stoddard yesterday and I picked up three new relays. Only because all the relays I have are old, or URO crap. ( all pass the headlight test) Obviously not a relay issue as the disconnect is leading to the relays. But I figured, why not?
Friday and yesterday the car stats and idled just fine. I'm hesitant to drive unless I have someone following with my truck for a pull home. Frustrating.

I'll look at the wire routing again today, but it seems like it's not direct.

[JamesM]

Thanks for the print. I thought I had it solved as well. Headed out for a 10 mile ride but turned around when I realized I had left my phone behind. Car died three times on the way back but restarted each time.

My home made OBD confirms the fuel pump circuit is the issue. during more testing we discovered that pin 14 and 12 do not always have 12V. And when they do we can't wiggle, jiggle, or bump anything to recreate the disconnect.

We were at Stoddard yesterday and I picked up three new relays. Only because all the relays I have are old, or URO crap. ( all pass the headlight test) Obviously not a relay issue as the disconnect is leading to the relays. But I figured, why not?
Friday and yesterday the car stats and idled just fine. I'm hesitant to drive unless I have someone following with my truck for a pull home. Frustrating.

I'll look at the wire routing again today, but it seems like it's not direct.

Old relay boards can cause a lot of problems which is a real pain given no replacement is available.

One issue that I have seen a few times that causes intermittent fuel pump failure that was difficult to track down was the connection between the spade on the board for the fuel pump relay ground trigger and its trace to the relay on the back side. These two components are basically press fit together and the combination of pressure from the connecter being installed combined with heat and vibration will cause it to fail intermittently while driving but test fine on the bench. To find the failure you have to back probe the forward left side pin on the 4 pin d-jet harness connector while it is plugged in, and pin 86 (driver side most pin) on the fuel pump relay socket. While doing this press on the connector and wire/pin to see if you lose continuity. This has to be done with the connector on, and potentially while everything is hot as it is the pressure on the pin that causes the connection break.


The spade that says "Ground to enabled fuel pump relay" in the first picture. To repair it you have to get to it under the potting material on the back side of the board. Be sure to test again after repair as a good repair can be difficult. Its tough to get enough heat into the junction to avoid a cold joint without melting the board. I like to use a deoxidizer on the metal prior to solder as well.