From: Neil E. Amrhein (neil@compu-powr.com)
Date: Wed Jun 04 2003 - 05:05:25 PDT
Jim,
It does sound like an air restriction, but since you eliminated that, I
would look for the fuel restriction. Change the filter. That will probably
fix it. If that does not fix it, I would take a look at the rubber fuel
supply lines, especially near the lift pump. I have seen (as the motor
mounts age and allow more flex), the rubber supply line get slightly kinked,
which limits the fuel available for higher RPM's. Shifting of the motor
(acceleration, curves, etc...) can also make it worse and cut off the supply
temporarily.
The other source for a fuel restriction is the filter sock in the tank.
That's a little harder to check though... Of course, you could always pull
the supply off of the lift pump and blow compressed air back into the tank
(with the fuel cap off) to try and clear it out temporarily.
When it hesitates, does it blow out any smoke at all (white or black)?
Are you running the stock 195 t-stat? To be honest, 215 to 220 sounds a
little high, especially given that you are running a turbo (unless your foot
is always to the floor!). If it is a fuel restriction, it should run cooler,
since it is getting less fuel. Of course, my stock '88 Crew Cab 6.2L 4x4 w/
4.10's and no OD usually reads about 205-210 at any speeds (195 t-stat), so
it could just be that the stock gauge is off (what a surprise that would
be!).
Unfortunately, that's about all I can think of to try right now.
Hopefully, someone else may have some other ideas, but I think the fuel
filter may be the whole problem.
--Neil
----- Original Message -----
From: "Jim Newton" <jnewton@laurel.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Wednesday, June 04, 2003 3:09 AM
Subject: [MV] CUCV Hesitation at Moderate to High RPMs...
>
> First, what a fantastic group of people we have participating in this
> list! Hats off to all of you! It feels like we have a big motor pool
> hall that we can just mill into and shoot the breeze and get answers
> to our pressing MV questions. How amazing!
>
> OK...chill out, Ike! ;)
>
> On my trip to LA this weekend, on the way back my "M1007" began to
> hesitate at around 60 MPH. It didn't want to go faster than that
> (probably OK since I had a stack of brand new deuce sideboards and
> troop seats hanging out the back open cargo doors). If I was going up
> an incline and I shifted down to 2nd Gear, the hesitation would occur
> at the same general RPMs as when it was in D (Drive) at 60 MPH.
>
> Usually this M1007 will step along quite nicely at literally 80 MPH
> with plenty of punch left (thanks to the Banks turbo installed by the
> previous owner on the brand new GM Goodwrench engine).
>
> There was no overheating problem despite the 100+ outside air
> temperature (OAT). It was running right at 215 to 220 degrees water
> temperature on the stock gauge, well below the red zone (240 is in the
> danger zone on this gauge). It typically runs between 200 and 220 on
> this gauge (not like the deuce which NEVER breaks 180 even towing the
> M1007 up a big hill). The EGT gauge reading was also quite normal.
>
> At a rest stop I popped the air filter element out and tried running
> without any filter, thinking maybe the air filter had become clogged,
> but still got the same hesitation. Dirty air filter eliminated as a
> cause.
>
> This happened with two separate fuel tank depletions and refills, so I
> do not suspect bad fuel.
>
> The truck runs fine and fairly powerfully up until mid to high RPM.
>
> It got decent gas mileage on the return trip (about 14 MPG) which is
> normal for this vehicle.
>
> Today I picked up a new fuel filter at NAPA (only about $16) but have
> not installed and tested it yet to see if that solves the problem.
>
> Has anyone experienced this type of problem? What was the solution?
>
> o Dirty fuel filter? (If so, my purchase will solve the problem)
>
> o Water in fuel? (would cause complete shutdown, not hesitation)
>
> o Plugged injector(s)? (would be rough all the time)
>
> o Turbo failing? (boost gauge read normal boost levels)
>
> o Electrical problem?
>
> I did notice lately (for the last 2 months or so) that when I would
> round a bend or change lanes on the freeway, the motor would hesitate
> a little bit. It startled me because it felt like I was letting off
> on the gas. Now it is like that all the time at 60 MPH. Maybe this
> will provide a clue to some sharp list member.
>
> Thanks!
>
> --
>
> Jim "Ike" Newton
>
> o 1984 M1007 CUCV Military Suburban
> 6.2 Liter (378 CID) Turbo-Diesel Engine
> 5/4 Ton Cargo Capacity, 4WD
>
> o 1971 M35A2 Military Troop/Cargo Truck "Deuce and a Half"
> 478 CID Turbo-Diesel Multi-Fuel Engine
> Air Shift Front Axle
> 2 1/2 Ton Cargo Capacity, 6WD
>
> See These Trucks at www.CUCV.NET
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