poor milage

[DLang]

new IP, new injectors (well, 7 new + 1 old, one of the new was bad, causing a knock), timeing set. Since I got the truck running thursday night I've put about 500 miles on it and am only getting ~10mpg!!

tomorrow while it's light I'll try to see if I have any return lines that are leaking fuel, what else should I look for?

[john8662]

Does sound like a leak. If anything your fuel economy under light highway driving should have increased.

What kind of smoke are you seeing? Heavy black under acceleration?

J

[DLang]

I definantly expected it to increase. I've put 10's of thousands of miles on these military blazers and I was routinely getting 28mpg or so with them. I've been very unhappy with this truck getting me 16-18, but when I found the IP problem I figured that was the cause (and finding this weekend when I went to go offroad that one of my front hubs was locked the whole time, the P.O. had turned it 90 degrees from locked to where the paint lined up, but not the other 180 needed to finish unlocking it :( ) but even after finding that the milage is dismal.

It's not putting out a significant amount of black smoke (not enough for me to notice in my mirrors), I'll have to ask someone to follow me to get a real check of it.

[john8662]

16-18 MPG sounds pretty reasonable for one of these trucks. Afterall it's a non-overdrive truck. so the RPM's are up there, especially on the open road.

The civilian blazers had overdrive (TH700 tranny) so they would do better, that is if it had 3.08 gears.

J

[Robyn]

Who did the IP and what specs did they set it to?
If the rig has been running ok what was the reason for the new parts??
If you were losing that much fuel it would stink all over the truck and you would see some leaks on the ground.
Very currious indeed?
I have an old 84 that has a bad IP and sour injectors and it still gets 16 in town???
Something is really amiss.
Keep us informed

Robyn

[DLang]

the new parts are becouse the overflow from the IP started clogging up on me every day or two, I figured that it was probably a smart thing to replace the injectors at the same time (figuring that what was clogging up the overflow was probably going into the injectors as well)

I got the new pump from Dumas Diesel in Long Beach, CA. I don't know what specs it's setup to, but the part number on the pump was cross refrenced to specificly fit a 1986 CUCV.

the reason I'm not happy with the 16 or so mpg is that I've spent a lot of time driving these military blazers in the past (quite a few different trucks) and would routinly get in the high 20's (other people getting into the same truck, driving the same route would only get around 20, so I'm _very_ aware of how much a difference driving style can make)

after getting things running last week I headed out on a lengthy trip over the weekend (Simi Valley -> Barstow->Baker->Barstow->Simi), I filled up three times for ~15 gal each time and was only doing 160ish miles between fillups (past years with military blazers on this exact same trip I've made the entire trip on a single tank and filled up when I got home) one leg of the trip was in caravan with a 1980 VW Vanagon, which could do 65-70 with a tailwind and 45-50 with a headwind (same road different directions :) ) so it's not a case of me doing high revs on the engine the entire time.

there more of a smell of diesel around the truck then I really expect, but I've been driving gassers for the last year so I am not sure if this is the normal diesel smell or an unusual amount.

I've been very happy with the anwers I've seen on this board to questions (my own and others). Thanks for the info

[john8662]

Hmm, next time you make a run, see if your speedometer and odometer are correct. take note of the mile markers on the highway and your mileage and see how close you are in mile intervals.

Maybe something is amiss with the speedo.

I wonder if the gears in the Blazer have been changed. With 3.08 gears (what they all came with) it could do pretty decent if driven reasonably (which you are).

It's possible that the differentials have been swapped out, or the gears changed internally.

Just more to check.

Any leaks found, park on the clean part of the drive way :D

J

[DLang]

I was running a GPS the entire trip and was takeing the distance and speeds based on that. I've got a tiny-tac in the truck, and while I didn't have it running this trip (I shorted the power leads and burned the wires just before the trip) my rpm's are about right for 3.08 gears (allowing for a couple hundred rpm slop due to the non-lockup torque converter at freeway speeds)

I haven't had a chance to park it on the clean part of the driveway yet, but no obvious leaks yet :confused: