12V problem, rough running, dies

[Grumpy8811]

We’re talking dinosaur 12 valve tech here grumps, no electronic throttle jazz on these mills.

OP have you tried the ‘ol pinching off the return line trick to see if it clears up your issue?

yeah, my bad.. a little early onset geriatiric dementia on my part for mixing this one up with a different thread about idle problems and all the graphs..

 

[raxley]

They ordered the wrong part, but it turns out they had one in stock, but its $140.i guess it's a genuine Bosche part, that's why. Anyway, I dont want to spend $140 if I can avoid this, and have a tork tech on the mail.
How do you stretch the spring? How do you take it apart?

 

[Signal73]

To my knowledge only the OFV that look like this can be adjusted

 

[BigPapa]

How do you stretch the spring? How do you take it apart?

Take bolt out of the top and remove the spring. There is a ball under the spring, make sure you don’t lose it. The ball shouldn’t come out. Measure the spring, then stretch it until it’s about an 1/8” longer than it was. If I remember correctly, it should be around a 1/2” long.

Have you tried clamping off the return hose as @Signal73 said? That’s the standard test for a bad overflow valve.

 

[Signal73]

Take bolt out of the top and remove the spring. There is a ball under the spring, make sure you don’t lose it. The ball shouldn’t come out. Measure the spring, then stretch it until it’s about an 1/8” longer than it was. If I remember correctly, it should be around a 1/2” long.

Have you tried clamping off the return hose as @Signal73 said? That’s the standard test for a bad overflow valve.

He appears to have a replacement without the nut on top. I saw these offered for sale back in the day when I had my 12v’s

 

[Grumpy8811]

Take bolt out of the top and remove the spring. There is a ball under the spring, make sure you don’t lose it. The ball shouldn’t come out. Measure the spring, then stretch it until it’s about an 1/8” longer than it was. If I remember correctly, it should be around a 1/2” long.

Have you tried clamping off the return hose as @Signal73 said? That’s the standard test for a bad overflow valve.

reminds me of how we did it on Harleys on the oil pressure relief valve, some people would stretch the spring, others would shim the spring with a small washer..

 

[raxley]

When I replaced the overflow valve last time, the valve isn't able to be taken apart.
I spent the $140 on the new Bosche one. Truck runs great now (or ran good for rest of the day yesterday. When I drove to work yesterday, it barely ran) the taller Bosche version was harder to get in, it's about 1/16" too long and it was difficult to get the second sealing washer in, but it's done now!
Thanks much for the help, TDR!

 

[Signal73]

When I replaced the overflow valve last time, the valve isn't able to be taken apart.
I spent the $140 on the new Bosche one. Truck runs great now (or ran good for rest of the day yesterday. When I drove to work yesterday, it barely ran) the taller Bosche version was harder to get in, it's about 1/16" too long and it was difficult to get the second sealing washer in, but it's done now!
Thanks much for the help, TDR!

For future reference the notch in the plenum can be ground out deeper to facilitate easier removal/install.

Glad to hear the situation was not as dire as you were thinking in post 1!

 

[raxley]

Although when I first got the "genuine Bosche overflow valve" ($140+) it started great and ran good for a few days. I got the Tork Technology overflow valve in the meantime. Then yesterday, it had the same problem. I looked at the gauge on the fuel filter housing and at idle, it was down to 10# again. So I ground the manifold (thanks Signal 73) and the overflow valve went in without a hitch. Started it up and the gauge is bouncing around 35#, and it didn't do what it was doing earllier, running erratically.
I need the snubber now. Anyone know whether to use a 12 mm or 14mm snubber? I'll measure it, and order it.
I've got Larry B's clear fuel lone that goes in between fuel filter canister and the P7100. I'm going to put that end next time I have a minute. I'd really like a inside gauge, I guess any of the isspro gauges or other mainstream gauge manufacturers make one that doesn't bring the fuel inside the cab.

 

[GAmes]

Forget the snubber, they rarely work correctly. A better fix for the lift pump pulsing and ruining the gauge is a needle valve that is barely cracked open. The line on the left is a grease gun hose. On the left is the Isspro sender to the fuel pressure gauge.