here we go again

[steve-r]

why do these symptoms seem familiar?
-a small, single intermittent hesitation when applying the throttle, just after the bottom of a hill, as acceleration passes thru 80-85 km's/hr...this goes on for a couple months
(scrath head : is it fuel starvation, TCC lockup?, bad OPS?, bad lift pump? )
-next, some colder mornings , harder starting, big puff of blue/grey smoke w. rough idle, then it calms down ... seems to get worse each morning over the course of about 2 weeks
-finally, today, it throws a code - 36

Fortunately, i'm still under the pump warranty....this will be pump # 7

I just purchased a new lift pump, OPS, and the material for the Relay mod, but i didn't even get a chance to install it. what does a guy have to do to manage this problem better? - i added the extra Racor filter to eliminate any possible tank contamination but GM has tested the tank and never complained of any, i change both filters every 7500 kms instead of 20000 kms, i add Stanadyne Lubicity formula to every tank of fuel, i added the FSD cooler and relocated the PMD to the manifold when the last warranty pump went in, and i dis-assembled, cleaned, tested, and re-assembled the stock fuel cap to ensure it will vent inwardly...i even crawl under and feel the lift pump monthly to ensure its still working, and i open the petcock monthly to ensure no stall.

so i'm scratching my head, wondering why so many pumps...and then it occurs to me that i noticed one more symptom...over the summer, when the fuel tank level got below 1/4 tank the last couple fills were preceeded by a big whoosh of air sucking into the tank..EVEN though I had serviced the fuel cap.... i don't know if this vacuum condition is exacerbated by temperature change ( still warm days here, cooler nights ) , but somehow it has got to be a factor in weakening or adding stress to what is already a very fragile fuel system. this also does not provide any conclusive evidence of why so many pumps/PMD's have failed in my truck.

I guess i'm just re-stating what many others have experienced in whole or in part, and suggesting that its not enough to just do a goodly portion of the additional preventative maintenance that I've learned about here on this forum. maybe I need some luck too!

[markrinker]

Seven pumps? You have more patience than I do.

Interesting theory on the vacuum created at the tank. My #1 creates the opposite - slight pressure. Cap has been replaced with same results.

Here is my theory: What differences are there between US and Canadian fuels?

[Hye]

Have you ever done an autopsy on the failed pumps? Is the failure electrical or mechanical? That might be a clue as to the real problem.

[Turbine Doc]

As a test, why not try a hard wire for power direct to the lift pump, that will eliminate OPS & PCM from the loop, put 12v on a toggle switch and power to the hot side of the pump and another jumper to the gnd leg of the pump to the frame, drive that way for a bit, then you have isolsted problem on the power side of the pump,

also, hook a temporary gauge with some rubber tubing to the drain cock valve of the filter bowl open it while driving and eyeball what the pressure to the IP is, should be 4+ psi maybe dip to as low as 1 on hard acceleration or hill climb but should recove to around 4 after coming back to cruise load on engine.

[steve-r]

Hye, all the pumps have been done under GM warranty, and they (dealers) don't do any analysis. in fact now they're just supposed to smash them, they dont even send them back to stanadyne anymore.

i think the first 2 or 3 pumps were mechanical, but the last few were more likely PMD's. as you know, GM doesn't distinguish, they just replace both whether you need it or not.
a stanadyne dealer told me with the last stanadyne pump upgrade to ceramic rollers, they don't get too many mechanical failures anymore unless tank contamination gets in there. most failures these days are electronic ( PMD ).

maybe i need a spare PMD to plug in to see if the problem goes away, but i'm probably not going to make that investment until my pump warranty is finished. for now, its drive it to the dealer, have an informed debate about the issue, they keep the truck for 2-3 days, and then its fixed.

anyone had any problems with dealers honoring the pump warranty when the PMD has been re-located on an FSD cooler?

[gmctd]

Vacuum in the tank is resulted from warm fuel cooling.

Pressure in tank is resulted from cool fuel warming.

Greater empty volume effects pressure equalization to Baro.

What temps are we talking here, at night?

DTC36 is Closure Time Long, where fuel solenoid may be dragging from thickening fuel.

Can also be caused by low power supply voltage to injection pump, from bad connection in hot wire, as well as in ground wire.

Check your engine bay wiring - battery cables, grounds, engine harness conectors, the Fuel Solenoid ground on top of the inj pump, etc, for corrosion, oxidation, loose connection.

Check the main PCM harnness wiring thru to where it goes into the lower passsenger-side firewall.

Your truck system is more than likely the culprit, not the pump(s).
I wonder if they've been replacing the pump harness with each new pump, or leaving the oem harness in place.

[ 09-26-2004, 02:37 PM: Message edited by: gmctd ]

[steve-r]

typical september temps for the west coast - Vancouver - are day highs of 16-20C or 70F, and at night 9-10C or 50-55F, so not a big swing.

different dealers have done the pumps, and i've never heard any of them talk about the electrical harness being replaced. if they don't come as part of the warranty parts list, then likely never.

i'll don't see any corrosion, but i'll keep an eye on it. 14.52V at the battery when engine running.

just pulled the high idle temp sensor plug, and the cold start was very smooth due to the longer glow cycle....also minimal blue/grey smoke. the longer glow cycle is compensating for the pump/PMD issue.

[gmctd]

Try taking the voltage measurement over on the fuse box with the battery as ground point, then the engine block as ground point, then ground point at relay panel.

Then try voltage reading in +12v supply wire at inj pump, with inj pump as ground point.

Low voltage\poor gounding will cause DTC 36.

[steve-r]

grounds checked out ok.
GM approved new injection pump today....#7 !!
this means they will have spent approx $20+K Cdn in warranty repairs for pumps on my truck.

diagnosis - fuel solenoid inside pump is shot. metal contamination has collected around it and affected operation. in turn FS draws more from FSD, FSD heats up more with higher power consumption, and eventually cooks itself, even if on a cooler.

this time i'm participating reluctantly.
while i think its bogus, and the dealer agreed with me, GM TAC would only agree to the warranty pump if I agreed to drop the tank and have it cleaned.
apparently they blew air pressure into the return line, stirred up all the stuff in the bottom of my fuel tank, sampled the fuel, and claim they found metal. i argued that my Racor 645 10 micron ( clear bowl was clean as a whistle ), and the OEM Stanadyne 5 micron would keep it clean ( no sludge at all in bottom under filter ) even if there was stuff in the tank. they argued that it is from the blue tag pumps when the rollers disintegrated ( bluetag were non-ceramic rollers), and that some of it is smaller than 5 microns.
i had 2 blue tags after the original. they also argued that the 5-10 micron pieces could
be pressured right thru the stanadyne filter, get inot the DS4, and wreak havoc & undue wear over time .in my case i'm averaging 12 months for a pump lately.
so why doesn't GM install a better 2 micron filter like the Duramax? no answer to that one.

he said...she said...woulda...coulda...shudda...all my arguments were for not. with 7 pumps they argued that something else was wrong, and that all other high ( i guess 7 is high in 130k Kms!!) re-curring pump failure situations had been proven to also have metal in the tanks.
i took one more shot at them and suggested that since they can't prove the metal came from where I fill up, then they can't argue with and even admit the fact that the metal came from their manufacuring problem....therefore the metal comtamination remedy should be included in the pump warranty. the dealer said " i agree with you 100% but GM is not acknowledging this fact"....so the dealer stays the nice guy trying to help me, albeit a bit transparent, and he blames those nasty GM TAC people....not an answer but i'm supposed to feel better....LOL

ps. in case you're thinking "take it to another dealer" i dont have any other dealer options here...most of them here in Vancouver only have parttime diesel mechs, and I've been to them all. some just don't know what they're doing. at least this one declared up front he didnt care if my FSD was mounted on the cooler or pump re. warranty elegibility.

so I'm no rocket scientist, but $500 for a tank cleaning, or $3K for a pump is an easy decision.

so they will drop the tank, have it chemically cleaned, flush the lines, replace the injection pump, lift pump, and both fuel filters, so that all parts that could possible hold metal contamination are corrected.

my pump warranty times out ( 11 years ) in April, so either this fixes it, or the Sol-D PMD replacement from Remarq proves to be a longterm solution, or I hope that Toyota hurries up and brings the turbo diesel Hilux engine to NA in the Tundra body...ha..ha!

ever faithful!

[norm]

Random Thought:
What about installing a filter on return line back to tank? Let's see how much metal a wearing IP will send back...

Has anyone done this?

[catmandoo]

well stanadyne and gm screwed up,but they sound just like politicians,blame it on you for not keeping the metal out of the fuel etc,etc.i look at gm and think they are the biggest piece of you know what,why the heck can't they build a diesel engine,man those cummins have balls run forever get fairly decent milage,what do we get an under powered pump failing block cracking,headgasket blowing anemic piece of junk..this should be a major recall issue.when mine goes again,its getting a mechanical pump i'll cure that problem lickety split.