What's wrong with my Suburban?

[6.5TD Burb]

Finally nice and not snowing or raining so I checked the recommended wires in the OPS thread. Reading a nice steady 13.9volts. That's with a new OPS and still getting the intermittent miss.

Did however find that the gray wire had a piece of insulation missing almost at the relay pigtail about 5/8" long and when found rubbing up against another wire. Taped that up, hoping that was part if not the problem.

 

[Pruittx2]

Being a 94 you should really do the OPS relay mod, If your OPS isn't toast yet,, it will be soon. The OPS relay mod, will keep you from having to replace the OPS every 8 months or so. check out the FAQ's for a how to on that mod.

 

[Sunshine]

Mine was doing the same no codes nothing, Bill Heath told me to do a flow test put a tube on the t-valve at the front put the tube into a clean container that will hold at lest 3 quarts open the t-valve 5 full turns start her up for 2 minutes no more & no less you should have 3 quarts of diesel in the container....you can also check you've got at lest 13 volts coming from the LP...Mine flowed for 30 sec and stopped, found out the top of the fuel sender was "Missing some Rust" & sucking in Air...

 

[Missy Good Wench]

Put a clear hose on the return from the top of the IP and loop it up by the wipers (leave the hood on the safety latch.

Give it a go and see if you are getting any air bubble streams.

If air is present that is probably the issue.

Plugged tank sock, bad connections at the tank.

Now doe it make any difference if the tank is full or near empty as to the fishbite.

If it only does it at low tank levels then the issue is the safety valve in the tank that will allow fuel to enter if the sock gets plugged. These are a spring loaded valve that opens if the sock gets plugged. When the fuel level goes below the valve (1/4 tank) then air is sucked in.


Let us know


MGW

 

[6.5TD Burb]

Problem found. The hardwire that I thought was used in conjunction with the OPS, the wire that I wasn't using, was THE power wire for the lift pump. If that wire as not "hot" the lift pump was not on; so I've been running on solely the injector pump as far as I can tell. Hooked the lift pump back up through the OPS and all seems to be fine, even after an hour of driving.

 

[Matt Bachand]

Thats great. This is one of the reasons I love my fuel pressure gauge so much. The truck can run just fine with a non working LP, causing extra stain on the expensive IP!!

 

[chefmike]

If it only does it at low tank levels then the issue is the safety valve in the tank that will allow fuel to enter if the sock gets plugged. These are a spring loaded valve that opens if the sock gets plugged. When the fuel level goes below the valve (1/4 tank) then air is sucked in.

MGW

HOLY CRAP! This totally explains why my wife "ran out of gas" and refilled to 32 gallons of fuel.

So my sock is plugged... and I can only run it down to 10 gallons in the tank... sigh. Siphon out the rest, drop the tank. Change the sock. And ???

 

[Veg_Out]

HOLY CRAP! This totally explains why my wife "ran out of gas" and refilled to 32 gallons of fuel.

So my sock is plugged... and I can only run it down to 10 gallons in the tank... sigh. Siphon out the rest, drop the tank. Change the sock. And ???

Throw the sock away, and put a prefilter on before the lift pump.

Maybe light it on fire for fun.

 

[Matt Bachand]

Throw the sock away, and put a prefilter on before the lift pump.

Maybe light it on fire for fun.

x2.

Be sure the sock is out of the tank before lighting on fire.:thumbsup:

 

[chefmike]

x2.

Be sure the sock is out of the tank before lighting on fire.:thumbsup:

Geez... without you guys, look where I would be ):h

Any suggestions for economical set ups? It looks like $200? I am doing so many other things right now to get the truck up to speed.

 

[Matt Bachand]

Walbro lift pump around 100, Refirb Racor from PBTXXX on ebay 60 bux (super deal) ,

PMDCABLE.COM Sells some GM Lift pump bypass fittings which allow you to remove your factory pump, use the fittings and the barbs to hoses so you don't have to modify your factory plumbing.

20 bux.

Fuel pressure gauge is the icing on the cake. 80bux.

Never hearing your wife complain that shes always worried of running out of fuel again.................

Priceless!

 

[chefmike]

Never hearing your wife complain that shes always worried of running out of fuel again.................

Priceless!

Of course that will require fixing the fuel guage when I drop the tank. Reads overfull to half tank mark, staying at overfull for the first half of the tank.

Thanks for the sources on that stuff. I appreciate the help.