Help lost my MPGs

[bbilt]

Newbie here, need a little help
Lost MPG after VE injector pump rebuild. I’ve had good experiences at NTG Racing up till now. Time to rebuild the injector pump so I took it to NTG Racing, it was leaking bad. I just ask for good mileage and no performance up grades. I was hoping that it might improve my MPG of 16. They sent the pump out to Omega for the rebuild. Got the truck back it seemed OK until I filled the tank and checked the mileage. Holy crap 12 MPG. I have never got that bad a mileage before. It was always around 16 MPG . Well took it back so they could figure it out. They gave it back to me after some adjustments to drive, wow now I could watch the fuel gauge move, 9 MPG. I took it back, they were stumped. They checked other components. “Everything checks out fine. “ Its got to be the injectors,” OK if that fixes it I’ll pay, if not I won’t pay for them. They didn’t change the injectors. They drove it and adjusted the fuel screw on the pump (per the rebuilder Omega) that brought it up to 10.5 MPG we’re not even back the 12 MPG I got at the first try. So is it the pump or is it the injectors? I removed the injectors and had then tested (Advanced Diesel) they tested OK, not the problem. As they had a little over 100,000 miles on them I had them rebuilt. Reinstall them and no change. NTG took the pump out and had it tested (Express diesel) a Bosch Certified center. The pump was taken apart and inspected. Not all the worn parts had been replaced. But still OK . Reassembled and ran on their test machine and readjusted to factory specs 1.25 then advanced to 1.45. Reinstalled ( with a dial indicator) in the truck and now I have it back. It seems ok, a little less power. Put some freeway mile on it and I got 12.65 MPG. Not the decent MPG I had before the rebuild All I want is my 16 MPG back. I’m losing 4 to 5 miles per gallon that adds up quick. What have they done to my truck? And they are still stumped. I still think it’s the timing. Joe said he doesn’t want to see the truck again. Now what? Searching for the answer
1992 w250 auto, gauges, 16cm 4" exhaust the rest stock 103,000 m & no smoke
Thanks Bill in San Diego

[Remps]

Could be the dynamic timing isn't working for some reason? Not sure if that is even possible though. I'd push it to the head and check mileage again.

[RCCUMMINS89]

That would of been looked at when bench tested.

The first question I would of had is... are you putting the pump on? As it is not an uncommon thing for the keyway to not lign up correctly and timing to be off. HOWEVER, it has been off a few times and that would of been (should of been) noticed. This is a correct assumption by me, correct?

Next thing.....is it running rough? Smoking (white/hazy) at all, at any time?


From what I'm reading, you have always gotten 16mpg (even up to the last tank) and then did pump and next tank as 12. Correct? didn't pull the pump because it was leaking and fuel economy was dropping?

[bbilt]

I had NTG Racing do the remove and replace the pump,they had Omega do the rebuilding of the pump. Pump was leaking real bad. NTG Racing reinstalled it using a dail indicator. The pump was advanced from stock of 1.25 to 1.45. I was getting 16 MPG before the pump rebuild and 12 MPG after. I was hoping for maybe better mileage with a fresh rebuilt pump. Truck runs good and it dosen't smoke.(just a puff at startup)
Question: If the pump it self is advanced can I safely advance it some more by turn it to the head?
Searching for my MPGs
Bill in San Diego

[oldestof11]

Auto or stick?

9mpg is unheard of! How well is the AFC adjusted?

[Tacoclaw]

Is it smoking or down on power or anything? Does it sound different at all? I know you answered earlier, but if it's not dumping falling of fuel on the ground I just don't see a MPG drop like that happening.

Do you have pyro/boost gauges?

[bbilt]

Thanks for the reply: The pump was stock going in and after the rebuild. So what happen?????
I not smoking has good power starts right up. No leaks of any kind found. Its a automatic. Gauges yes, RPMs below 2000, good boost. Had been getting 16 MPGs then the pump started leaking bad, took it in for repairs. Pumps been off & reinstalled 2 times with no changes to the MPGs. I'm not sure what they did when it went no to 9 MPGs, you could watch the needle move, but they got it back to 12 MPGs, but not back to my 16 MPGs.

Searching for my MPGs
Bill in San Diego

[oldestof11]

Could be that your converter took a crap at the same time...

[PToombs]

I'm wondering if they nutted the pump to make sure it won't smoke, he is in California after all. More power usually gives better mileage so it's possible.