'79CA bus intermittantly wont start, fuel pump not triggered

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airkooledchris
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Location: Eureka, California
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'79CA bus intermittantly wont start, fuel pump not triggered

Post by airkooledchris » Fri Jan 03, 2014 1:15 pm

On my summer project bus, also a 79 California import, ive ran into this problem 4 or 5 times now.

Symptom - it won't start.

I leave the key in the ignition, go back and pop the lid off of the AFM and move the swiper - you can hear a very distinct 'CLICK' - but no fuel pressure is seen.

The first few times I simply unplugged both connections to the double relay, plugged them back in snugly, wiggled the little ground wire that grounds to the double relay mounting screw, and fuel pressure returned.

On new years day, at around 3:30AM of course, it pulled this on me again. This time the old trick didn't work. I started to fiddle around trying to find where all of the wires to/from the relay are going - and at some point I wiggled the cluster of wires heading back through the firewall towards the fuel pump and it worked - for just a second. I couldn't repeat this.

Next I crawled under the bus to check the wiring at the pump itself. I have a barely lit flashlight (and mind) at this point, but im just feeling to see if the two wires going to the fuel pump are still connected snugly. I try also to just track where the wires are coming/going, to see if anything is obviously split/broken/whatever - but for the most part I just touch everything and give it a little wiggle. Nothing seemed obviously out of place.

After this last attempt under the bus at the fuel pump, now it starts right up and I again have fuel pressure.

With it only happening intermittently, I am not sure how to move forward with preventing this in the future. Should I just re-do the wiring at the fuel pump? Is this a sign the double relay is *starting* to fail? When it's working, which is 99.9% of the time, it'll pass all of the tests (right?)

I just don't want it to happen in an inconvenient time/place, like 3:30AM on new years day in a shitty neighborhood with all of my expensive Dj gear sitting inside (as an example.)
1979 California Transporter

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Amskeptic
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Re: '79CA bus intermittantly wont start, fuel pump not trigg

Post by Amskeptic » Fri Jan 03, 2014 3:30 pm

airkooledchris wrote: won't start.
AFM wiper - distinct 'CLICK' - but no fuel pressure
unplugged connections to the double relay,
wiggled the little ground wire
wiggled the cluster of wires heading back through the firewall and it worked - for just a second.
Visually verify that all terminals are seated in the white plastic molex plugs of the double relay. You have to verify that none get pushed down as you seat the plugs (sometimes the barbs get mushed and the terminal will not slide up the male spade on the double relay). Use dielectric grease on spades.

Clean and resecure the ground wire and the metal path to the firewall. If the screw strips in the firewall, get bigger screw, it must be secure and use dielectric grease on screw..

Then and only then do you check the wiring harness through the grommet to the pump. Keep simple and stupid for as long as you can.
ColinSimplyStupidColdInNY
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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