IP going, going, gone?

[kconnair]

I think the IP on my '86 Suburban 6.2 may be going south.... Truck starts ok, but once it really gets warmed up, power drops, and drops, and drops. Almost feels like the tranny is going bad, but the Way, Way "open" throttle condition is fooling the transmission. Cool down, and it perks back up - briefly. Seems to be making additional noises from the area around the IP.

Anyone agree?

Thanks,

Kevin.

[britannic]

A few questions to help with your diagnosis:

How many miles does the lift pump, IP and injectors have? Is your oil pressure good, once the engine's warmed up? How about the timing chain and engine timing?

[kconnair]

Oil pressure is excellent, new chain, gears, balancer, and pulley assembly. "J" intake.

Guessing that the IP and the rest of the fuel system has more than 100k - maybe up to 35k - 40k more. I figure that if it was just the lift pump, I might smell diesel in the oil, there might be be an external leak, and it would do it all the time, not just when it warms up. The IP starts making a lot of noise once the engine warms up. The engine was a swap done for the previous owner. The original engine was damaged by a transmission shop when they rebuilt the tranny.

[britannic]

Check the pressure from the lift pump; it should be around 7psi - lift pumps can weaken with age, without announcement :D .

As the IP wears, it can produce the symptoms you have noticed, ditto the injectors. The IP timing needs to be checked as well, since internal wear can cause issues with it.

[kconnair]

So, If I replace the lift pump at the same time as the IP, I should be ok. I only want the truck to last another year. I have a spare (good condition) injection pump.

I don't want to put the money into the injectors for this truck.

Kevin.

[Moses]

hey Kevin,

i am interested to know what happened here? because i supect my IP is dying too. . .
but i have opposite symptoms, my rig is very hard starting then smooth running.

i recentily changed the head gasket and took it a shop for timing, my guy told me the IP was shot when i picked it up, but it started right up for another week. starting is scketchey now, i guess i've got some more to learn about my rig this sunday.

so did you have to change your pump too or was it the injectors?

moe

[Moses]

well i guess Kevin's a no show, so far . . . but i am interested in what any one has to say about IP replacement because i am changing out my IP today.

This is new territory for me and i will take into consideration anyone's suggestions or advice


thanks,
moe

[britannic]

Hard starting can be caused by a number of factors - here are a few:

</font> Air leaking into the fuel supply before the lift pump</font> Faulty HPCA and/or glow plug controller/glow plugs</font> Worn lift and injector pump/injectors</font> Incorrect IP timing</font>

[dieselbegreat]

It's been said that adding some motor oil to your fuel can increase the viscosity and help a truly worn pump deliver better pressure and power. If this helps, it is only a temporary solution.

[kconnair]

It was weird, but my ip problem went away during trouble shooting. I changed the gas cap for one which I could pressurize the tank (to check for leaks between the tank and the lift pump. I swapped out the hose from the fuel pump to the IP feed line with a clear plastic one to check for bubbles. Away went the problem - Go figure :eek: The truck was running better than ever. Good power, running smooth, better top end and seemed to be doing better on fuel.

Drove it about 200 miles, and the next day, a woman in a hundai turned left in front of my wife, and totaled the Suburban. We were right in the middle of moving, so cutting our Suburbans from 2 to one really hurt. My wife was banged up - pretty badly bruised, but nothing really hurt, but the lady in the hundai went to the hospital with a head injury. If my wife had been going the speed limit of 45 instead of moseying along at 35, the truck would probably have rolled, and the other lady would most likely have been hurt much worse - not to mention possible injuries to my family.

The Suburban's sheet metal was rippled all the way back to the rear quarters, the front doors were jammed shut, and the drivers front wheel was bent back almost to the firewall. The Hundai was just a little shorter in the front - it actually looked a little better than the Sub, but the difference in the injuries really tells a tale.

Funny thing was my 7 month old daughter barely knew anything happened, all snug in the back seat in her rearward facing child seat. The loud noise upset her a little, but not a scratch or bruise. A testimony to a well installed and well chosen travel system. smile.gif

[britannic]

Very sorry to hear about the accident - thank goodness your loved ones are OK!

Moot Musings: I wonder if the original gas cap was venting properly? Was the original return line clear of obstruction? Did pressurization of the supply side of the fuel system, clear things up?