NEW ENGINE AND PUMP INSTALLED.PUM IS losing injection pump prime, is THIS A bad PUMP?

[asabadin]

Well after installing my engine and getting it running i am not able to get it to hold the fuel pressure. evereything else works, sylenoid is enaging and dis engaging properly plenty of fuel pressure from the lift pump and fuel filter/heater. bled the pump properly but it will not hold the prime. if it sits for a while i have to blead it all over again there are no codes on the scanner, the engine has never started under it's own power, only with spraying a fuel cocktail in each cylinder. once the engine gets to 2k rpms it cycles fuel fine. i still have not driven it so i cannot say what it will do whilE driving but after the truck sits for A WHILE AFTER RUNNING IT FOR AN HOUR OR EVEN LONGER, NO DISTRIBUTION FROM THE PUMP!!! PLENTY OF FUEL PRESSURE GOING TO IT. NO VISIBLE AIR IN THE RETURN LINE . WHAT GIVES ? IS THE PUMP BAD? IT IS NEW AND CAME WITH THE ENGINE HOPFULLY YOU GUYS CAN HELP

[ 03-02-2005, 04:43 PM: Message edited by: asabadin ]

[charliepeterson]

After it sits long enough to not start pull the fuel filter to see the fuel level in the bowl before you crank. It should be full. If it is full crack a few injector lines to see if fuel comes out. If fuel does come out then I would look at the engine timing. You may need to re-time it. Are the glow plugs working correctly? When you "add a fuel cocktail" you could be by passing some GP benefits.
A restricted fuel return line could give you trouble as well.

[ 03-02-2005, 06:49 PM: Message edited by: charliepeterson ]

[asabadin]

fuel level in bowl is fine after it sits glow plugs are cycling fine, there is fuel in the pump and return lines i used a clear hose to see if air would develop and none solid fuel. hypothisis?

[charliepeterson]

If you crack the #1 injector do you get good fuel coming out while cranking? Do you know what the timing numbers are?

[asabadin]

get plenty of fuel out of #1 . engine came pretimed and synchronized to the injection pump.

[charliepeterson]

If the timing numbers are close to zero this can make it difficult to start when cold. I run mine at -1.94 TDC.

[asabadin]

anyone else here have an opinion?

[Barry Nave]

It came timed.
Can you verafie this data while a scan tool is hooked up?
Once running, it does run good. Is this what I'm hearing?
If it came timed, then the Eng must of been ran in while hooked up to a PCM/ECM, though it was not your unit. (or was it?)
The TDC could be way off as would be the timing.
Just my thoughts.
I take it that we are dealing with a DS4 system.

[CareyWeber]

You have a leak in your fuel supply lines some where. I'd check all your connections again.

On the old mechanical pumps the throttle shaft seals would wear and then they would lose there prime and be hard to start.

Check to easy / cheap things first.

Carey

[asabadin]

ok guys thank you!!

[gmctd]

Any idea as to what type of truck it is?

What type engine?

Year?

Anything?

[asabadin]

97 block, 95 suburban 2500 6.5 td

[gmctd]

Excellent! You have an OBDII engine in an OBDI truck.
Check the Inj Pump for specific DS4 model number - it's on the aluminum tag, rear of IP.

[gmctd]

I'm turnin' blue, here, asbadin, holdin' my breath...................

[rjschoolcraft]

GMCTD,

The only way that would matter is if he had a 94 with an eprom for a 5068 pump. Am I missing something?

[gmctd]

Well, I didn't wanna spill the beans b4 hand, but.....

I've done an unofficial, informal, informed (depending on who ya ask!) study on NEW INJECTOR PUMP, HARD STARTING syndrome.

Many factors can effect this, but NEW PUMP is a specific, where the OBDI '94-'95 vehicle got a new\rebuilt late OBDII Inj Pump - the DB4-(8031)-5521.

In each case, difficult or extended starting is the result - engine runs well, no missing\stumbling, good power, hard starting.
Starts well at hot, if re-started shortly after shut-down.

Symptom is indicative of loss of prime, resulting from fuel drain-back.
Or, simply, de-pressurization\pressurization interval, with newly-installed fuel supply components.

This would tend to indicate some difference in the Inj Pump, itself, possibly some modification intended for the proposed 215hp upgrade.

Lift Pump operation is considerably different between '95 and '96.

OBDI lift pump runs in START, then OPS switches in under rising oil pressure.

OBDII lift pump, under PCM control, runs at key-on in WAIT TO START, during START, then under PCM and "redundant" (sic) OPS control.

'Nother words, OBDI is primed at only START event, OBDII Inj Pump is primed long before START event.

As low-pressure low-volume lift pump is at considerable distance from IP, with fuel filter cannister in-line, IP can\will require fuel before that volume can be pressured up.

New lift pump, filter, starter, batteries, etc, same complaint - runs well if it will start.

Could be PCM controlled IP operating differences, OBDI to OBDII, but modifying lift pump operation is first step in solving puzzle.
GM did so in '96.

I removed the Optic Sensor Filter, without improvement.

TechII indicates some operating parameter differences, apparently desireable in OBDII.

[rjschoolcraft]

That's interesting, but I may have a monkey wrench to throw into the works here.

My injection pump was replaced under warranty in 2000. I just went and looked at the tag... is is a DS4831 5521 pump. This is the latest configuration as far as I know. I have used it on my 95 OBDI set-up for 148191 miles. Never experienced this issue. I suspect something else is the culprit.

I would redouble my efforts to ensure no air is entering the system anywhere between the lift pump and injection pump.

[gmctd]

Fair enough - you're one....I'm one of many.

Why not start a poll on OBDI with 5521 Inj Pump replacement, and any associated problems.

Would need to include date code from tag on IP, to illuminate any production 'batch' problems.

Also, as 'hard start' is relatively subjective, the estimated time, crank-to-run.

Smooth idle\run, rough idle\run, excessive, normal, or no white vapor.

My truck always started within 1/2 crank revolution, summer or winter, with the 5288 IP, DSG gears, oem and Max-E-Tork chips, 8.5deg actual\desired, -1.5deg TDCO.
Initial white vapor puff in winter temps.

After 5521 install, starts within 2-5 crank revolutions cold, 1/2rev at immediate warm restart.

No dripping Diesel fuel, no wet seepage around supply tubing\hoses, no raw Diesel fuel odor, white vapor puff if 4-5 crank revolutions.

[ 03-04-2005, 04:55 AM: Message edited by: gmctd ]

[rjschoolcraft]

Maybe my definition of "hard starting" is different than yours. In fairness, I didn't drive this thing long enough with the original pump to be able discern the kind of difference that you're talking about. I would say that mine starts (at least before it grenaded) as your second description, but I never thought anything of it.

This doesn't sound like the same problem that asabadin was reporting, to me anyway.

Always appreciate your insight, so don't take this the wrong way.

[B Lake]

My brothers truck, 98 Sub, starts as soon as you touch the key. My truck, 95 Sub, cranks and cranks before it fires off. Sort of like it has a small air leak and needs to pump up.

For a test, I put the tranny in R and hit the key, the lift pump runs (as it should) If I had an air leak, this should help the cranking time. It doesn't do a bit of good, still cranks and cranks.