Help Lost my MPG

[bbilt]

Newbie just found the site, any ideas. Thanks 

 

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? 

1992 w250 auto, gauges, 16cm 4" exhaust the rest stock 103,000 m

[Mopar1973Man]

Boost leaks?

 

Injectors pop tested to spec or just in the "OK" range?

 

Some how it just seems that fuel isn't atomized good or timing is off a bit yet.

[bbilt]

Checked for leaks, non. Boost is 7-8 @ 65 mph on the freeway

Injectors rebuilt & retested good to spec

 

Thanks Bill     still looking for my MPG

[Mopar1973Man]

I still tend to look at the injectors. Being the spray pattern is poor then the atomized fuel will not burn clean. If the pop pressure is low then the spray isn't as fine and the timing ends up being advanced. I would see if you can hook up with a 12V owner here and see if you can swap injectors with some for testing purpose.

[bbilt]

They pop tested the injectors , they were between 200 & 220, a little low. They were rebuilt, they were at 260 I think thats on the high end? Tested at 2 different shops.There was no change in the MPGs after the injectors were rebuilt, so that wasn't it. 

I'm not smoking gray or black.

 

Thanks Bill  still looking for my MPGs

[Mopar1973Man]

Rebuilt? So the nozzles what was the quality of the spray? So did the nozzles and pintles get changed in the rebuild? Just because the change a shim on the spring doesn't change the spray quality replacment of the nozzle and pintle will.

 

So you can see how little there is to the injectors.

http://articles.mopar1973man.com/2nd-generation-12v-dodge-cummins/15-how-to-clean-your-injectors

[bbilt]

They said the spray ( good atom) was good . Both Bosch shops tested them and OK 'd them. 

Can injectors make that big a change in MPGs. Same injectors before and after the pump rebuild. What changed so much that I lost 4 to 5 MPGs. Filters all changed, no leaks found, good fuel. I have test drove about 1000 miles trying  and testing things with out any improvements.  Still looking for my MPGs

 

Thanks Bill in San Diego

[Mopar1973Man]

What has to occur is the fuel sprayed in a fine mist that the compression heat can covert from liquid to vapor to go BOOM! so yes spray pattern and quality has a bit to do withi it. Another one that can impact the MPG's is valve lash and compression. If the rings are getting weak and excessive blow by starts occuring then power is lost around the rings. Valve lash could do the same thing too being valves will open later typically because of wear of the valvetrain parts. I know you have low mileage on this but I'm now listing all the different things I can think off.

[dorkweed]

How heavy is your right foot???

[bbilt]

My foot didn't get any heavier. The only thing that changed was the injector pump rebuild. I'm looking for my 16 MPGs back or better if I can. Heard from others that they're getting muct better than the 16 MPG I had been getting. I have a friend that has a v10 Ford that get 12 MPG. Where did my MPGs go. New filters, valves adjusted, timing adanced a little. What kind of MPGs are you getting?

Thanks Bill in San Diego

[Mopar1973Man]

Even my buddies old 1992 Dodge 1st gen did better than 20 MPG. Sad part is that the injection pump and injectors are very very simple on these truck and something had been changed. Bad part is to set timing isn't easy for home owner because of the special dial indicator that is required. As for injectors it nothing more than a shim to control pop pressure but the nozzle will dictate quality of spray.

 

I wish you were closer to me I'd love to work on this issue and make it right for you...

[Hawkez]

How about other things like tire condition and air pressure?  Do you have a brake that is dragging?  Air filter condition?  Could it be bad fuel?

[bbilt]

Thanks for the reply:  air pressure good, new air & fuel filters, brakes & trans checked. I have run 4-5 tanks of fuel through it from different stations & no change. The pump was set with a dial indicator, so the timing should be right (so the shop says) I'm not so sure it right. I don't know what else to try. I have talked to other shops and they don't know. What could they have changed that changed my MPGs that much.

 

Thanks Bill in San Diego 

[Mopar1973Man]

Do you have gauges? Boost & Pyrometer? Might give us a clue to whats going on.

 

Thinking there is a KSB sensor on the manifold and a valve on the injection pump that open and closes depending on intake temperature. This will effect the timing advancement of the pump. Possible the sensor isn't working right and sticking the valve closed or open and not giving proper timing? That the thing that so tough about older trucks there is nothing to give clues of what failed because there is no computer to report the issue.

[Vais01]

I know this is an old thread but I am familiar with the VE injection pump. Chances are AFC settings(star wheel/fuel pin adjustment) are incorrect. Also another potential issue is static pump timing. If I remember correctly the timing can be adjusted by rotating the injection pump towards the engine to advance timing and away from the engine to retard timing. You can only shift it 1/16th of an inch on the retarded side and up to 1/8th of an inch to advance it. I always advance the pump 1/16th of an inch first as this does not affect towing performance. On the top of the VE pump there is a stamped line marking center and a line on the back of the timing gear case the pump bolts up to. That is what you gauge your movement on.

Let me know if you would like any additional information on pump adjustments.

Edited September 3, 2015 by Vais01