82blackstang

hi all ive just brought a 1992 astro lt ext and it will only start if you pour abit a fuel into the air intake then it will run ok until you try and put it in gear then it stalls ,if you give it some more revs and hold it on the brakes it will go and it will run fine with no ploblems until you go to stop and it stalls again .you need to pour the fuel in everytime you start (hot or cold).its has a 4.3 v6 efi z code lb4 with auto transmission 2wd.i will try and get the fuel pressure checked tommorrow.
if anyone on here has an idea of what is wrong then please reply or email me at damienstamps@hotmail.com
also what pressure should the fuel be?
what code reader do i need so i can check them?

thanks damien

CD Smalley

Fuel pressure should be 9-13 psi. When you test it make sure to try pincing off the return line. The pressure should spike. If it doesn't, your pump is weak and should be replaced.

__________________
CD Smalley

1991 W41 #142
1995 Astro
1989 Caprice 9C1
1997 C1500

1977-90 GM B-Body email list Owner @ yahoogroups.com

In the recovery room: b-body.org...

82blackstang

hi thanks for the reply i will get the pump tested first thing in the morning
has anyone got a wiring diagram that they could scan and email to me please thanks damien

82blackstang

hi i did a fault code test today and its not showing any faults.i also swapped the fuel pump relay and pcv valve form another van and it didnt make any difference i was going to bridge the feul pump but couldnt find out what colour wire i needed or if it was live(+) or negitive(-) to feed the pump,
i know i need to do a fuel pressure test but i havent got a pressure gauge yet and im not should where to connect it .as i live in england uk its hard to find a garage that can do it .any help would be great thanks damien

CD Smalley

Most guages that I have seen are installed in place of the fuel filter for TBI engines.

__________________
CD Smalley

1991 W41 #142
1995 Astro
1989 Caprice 9C1
1997 C1500

1977-90 GM B-Body email list Owner @ yahoogroups.com

In the recovery room: b-body.org...

82blackstang

hi i've checked the fuel pump is pumping fuel to the throttle body but i haven't checked the pressure yet, hopefully i will get that tested at the weekend but i did otice that when i'm cranking the engine the injectors aren't spraying any fuel in but when it is running they are spraying fuel.
is it possible to fit a carburetor onto my engine ?
or is it ok to fit an ecm from an 1989 astro 4.3 z code auto?
thanks damien

94&92Astro

http://www.automotiveforums.com/vbul...74#post4568574

Hey Damien you sound like me with my TBI about three weeks ago... check out the above thread. Pullin that freakin gas tank aint no fun, but if the starting fluid makes it run good...more than likely it's the pump or like in my case a 2 inch long fuel line that attaches the fuel pump inside the assembly to the outgoing line--there is two push clips on either side and because this was a carter replacement pump, the small black hose did not look like any fuel line I ever seen--was fat and spongy, like small pipe insulation. Gasoline slowly ate at the line till it resembled black bubble gum and sprung a leak or two causing the pump to get just enough fuel to the TBI to change and suspect every component in the doghouse--But the guilty party is in the tank!!! I have never seen this type of hose in the higher pressure models that do not use the TBI.

82blackstang

hi all thanks for the reply so far

ive had another look at the van this weekend i put a slick50 (oil treatment )in which has stopped the engine from knocking ,ive also cleaning all the earth points and connections it now starts sometimes and doesnt stall as much.

the ecm in van is a sevice number 16144288 auln *86aulnkb21491841* 16151111 and ive also got a 1988 astro with 4.3 v6 tbi engine and the ecm is service number 16144288 aumh *86aumhk300890391* 16151241

can i swap them over to see if that is the problem ?

thanks damien

Blue Bowtie

In my experience, ECMs typically do not experience intermittent problems. They either work, or they fail and remain that way. They sometimes experience poor circuit board connections due to thermal creep or external stresses, but usually don't simply fail on their own. ECM hardware failures are almost always due to external influences such as shorted outputs or system overvoltage. Intermittent problems are usually related to the connections at the ECM, the MEMCAL or PROM, or the ECM input or output devices. ECM connections can usually be improved by simply unplugging and reconnecting/reseating the connnectors several times to wipe the contacts clean and establish a new connections surface.

In basic design, the two ECMs are identical. The difference will be in the PROM. The '88-91 TBIs used a $4E hex ID sequence while '92-93 used the $A0. Both are for the LB4 engine. I wasn't able to find the BCC for either program AULN OR AUMH), so I cannot state whether they are compatible.

If you still suspect the ECM itself after diagnosis of the other parts of the system, you should be able to exchange ECMs, but use the PROM designed for the vehicle in either case. Pay particular attention to the orientation of the PROM and the plastic skirt/carrier before performing the swap.

The fact that the ECM will operate the injectors so long as you provide some startup fuel leads me to think that the ECM is doing its job. One way to determine this is to check the injector(s) for operating pulses during the no-start episode, and while the engine is cranking. If there are no injector pulses, either the ECM is not acting upon the input of the distributor reference signal, or the distributor reference signal is missing or weak. Since the ECM does operate the injectors after you have manually administered fuel, I would suspect the latter.

If injector pulses are present but the injectors do not spray fuel, you need to look at fuel pressure.

Also, there is a G.M. TSB regarding cold startup knock:

COLD ENGINE KNOCK - #37-61-05A - (Oct 1, 1995)

This is NOT a recall, and if it applies to your vehicle, is not done as a free service.

This TSB may apply to your vehicle, or may not. The "fix" is to retard ignition timing when cold to minimize cylinder pressure until the engine is warm and parts have grown to their design clearances, thereby minimizing cold knock. The later PROM you have may have this feature, but it also may not be appropriate for the axle ratio, injector size, and may be incompatible due to other variables.