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PostPosted: Fri Dec 21, 2007 12:58 am 
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Location: Denver, CO
Hi, just a quick (well may be kinda long) question. I'm working on a customers 81 luv diesel. Not sure what displacement, but i know its stock with a manual. It seems to have a little performance problem, at higher RPMS, maybe around 2000+ it seems to develop a miss. And not to mention a serious fall off of power. Its like it almost falls on its face. If you keep mashed on it it will completely plateau. It seems to idle well and power at low rpm is decent.
At idle tho it does have a poping noise out the intake. Now i know diesel intakes are very loud and I've heard poping out of diesel intakes before. On the old ford navistar 6.9s its related to worn out rocker arm pivot shafts. I've heard it on a powerstroke too once that had a bent valve, but it ran very well tho.
I also noticed that the if i take the air cleaner nut off with the clamps still on, it actually BLOWS air out in relation to the poping sound.
Thinking maybe valve train issues, or injection pump output issue, maybe a fuel filter, injection advance even? I'm really unsure on where to even start.
Thanks for reading my short story here and thanks in advance for anyones advice/help, I really appreciate it!

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1975 LUV with a caddy 500ci, 12.5-1 comp, 850CFM holley sucking E85 through 110 jets and torquing the hell out of a TH400. Currently @ 6mpg

Bowties may be for little boys, but ponies are DEFINATLY for little girls....


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PostPosted: Fri Dec 21, 2007 9:34 am 
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Location: Germantown, TN (right next to ElvisTown)
It is a 2.2 liter, that's the only diesel they put into a LUV (same as the Isuzu P'up). And it's a 5-speed, unless it's 4wd.

Do you know when this problem started? How long it's been going on? Any other work that was done before this started? It could be as simple as a tank of bad fuel. I'd start with the simple stuff before doing anything drastic.

Don't be fooled by the apparent blowing of air out the intake. I've held my hand over an air duct (in my house) and was SURE it was blowing, then I put a piece of cardboard over it and it sucked it down tight. I could be wrong, but I suspect it's like that.

If the customer can fill us in, it would probably help.

Jack

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PostPosted: Fri Dec 21, 2007 1:59 pm 
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from what i told its been going on for a very long time now, its just a grocery-getter rust-collecter intown truck. I was going to start with a fuel filter and then move into a comp test and/or leakdown, since thats simple

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1975 LUV with a caddy 500ci, 12.5-1 comp, 850CFM holley sucking E85 through 110 jets and torquing the hell out of a TH400. Currently @ 6mpg

Bowties may be for little boys, but ponies are DEFINATLY for little girls....


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PostPosted: Sun Dec 23, 2007 7:59 pm 
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sounds to me like fuel aeration. when i installed my new fuel cell i had a very tiny leak. just that little leak at the cell caused it to turn into foam. Did the same thing. ran good and strong at idle. get into it some and it lowers rpm and falls on its face. sometimes it even shut off. it ran like junk untill i fixed that. now it runs great.

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PostPosted: Mon Dec 31, 2007 8:59 am 
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I agree. There are several cheap things to check before you start tinkering with the expensive stuff like compression and the injection pump. An air leak ANYWHERE between the tank and the pump will produce symptoms similar to what you're seeing. So will a clogged fuel filter. If this happened after changing a filter, I'd say you introduced a leak somewhere.

There's also a debris screen inside the banjo bolt that supplies fuel to the injection pump. This sometimes clogs and causes power issues. It's not hard to remove and blow out with air.

Jack

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JoeIsuzu@IsuzuPup.com
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PostPosted: Fri Jan 04, 2008 11:01 pm 
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thanks for all the great advice. We did do a fuel filter, confirmed the integrety of the underhood fuel system, but no change. I did do a quick compression test, varying about 5psi +/- it was 300 on each. I did not do a leak down because i didn't have a 1 way cylinder insert for the tester...meant for a gas engine with spark plugs. So i may be condeming an injection pump, but not before i have a look in the tank.

Also, i know diesels vibrate, but this bad boy shakes the steering wheel out of your hands at idle! On the old fords you can tune them down in the pump and they'll smooth out, but i dont know much on the isuzus. I guess i only get to work on the stuff that breaks a lot.

thanks again!!!!!

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1975 LUV with a caddy 500ci, 12.5-1 comp, 850CFM holley sucking E85 through 110 jets and torquing the hell out of a TH400. Currently @ 6mpg

Bowties may be for little boys, but ponies are DEFINATLY for little girls....


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PostPosted: Fri Jan 04, 2008 11:03 pm 
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P.S. I also ran a can of BG248 in the filter and did a little redneck "purging". Still, no affect.

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1975 LUV with a caddy 500ci, 12.5-1 comp, 850CFM holley sucking E85 through 110 jets and torquing the hell out of a TH400. Currently @ 6mpg

Bowties may be for little boys, but ponies are DEFINATLY for little girls....


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