91 astro vin z fuel cutout/stall prob

wolf8963 · 08-12-2009, 01:25 PM

Here’s my problem: I hope you can help
The vehicle is a 91 chevy astro 4.3L with 100k+ miles
About 2 or 3 weeks ago, very occasionally at first, the engine would suddenly die. There was no warning , no sputtering, no hesitation, it would usually just die. But it would start right back up and run fine afterwards.

As time progressed, the problem became more frequent, and sometimes you’d have to grind a bit to get it restarted.
Yesterday it died on my wife and is now very hard to start and will only run a few minutes if you’re lucky.

Last night I pulled off the air cleaner and junk so I could see the throttle-body injectors. When it’s running they appear to be firing fine, then suddenly they’ll just stop firing and the engine, of course, dies.

I started by replacing the fuel-pump relay, which seemed improbable but was easy and cheap.

Next I replaced the fuel filter.

Then finally I installed a fuel pressure regulator diaphragm kit. I really thought that would be the one that
would do it – but no soap.

We had the fuel pump replaced about 2 years ago – supposedly with an oem (they certainly charged us for an oem) so I haven’t been looking in that direction.

But at this point I don’t really know where to go next. I would welcome any advice!

A side note on the fuel pressure regulator diaphragm kit. When I was installing it I saw something that looked strange to me. I have never had that area apart before so I don’t really know what normal looks like but let me try to describe what looked odd.

Picture the assembly that the spring and diaphragm fit in. Now flip the whole assembly over. At the bottom of the bowl there is what looks like a port – about half an inch in diamteter, that fits down into a hole in the throttle body.

What I saw was, looking into that port, it looked like a large glob of molten copper (or copper colored metal) was plugging the port from the inside of the bowl. It didn’t look machined, it had about the same appearance of if you took a large glob of molten solder and dropped it into water – roundish and rough.

Since there is a slot in the side of the bottom part of that bowl that a tab comes through – I think to lock the pressure adjust screw in place – it doesn’t seem like any gas would be going into that part of the bowl. So it doesn’t seem like the glob would matter. But I thought I’d mention it.

Thanks for your help!

CD Smalley · 08-13-2009, 12:28 PM

Test your fuel pressure. I'd suspect a weak pump first off. TBI must be 9-13psi.

Next would be an ignition module. Get the pressure first before you throw parts at it an further.

wolf8963 · 08-13-2009, 01:12 PM

Quote:

Originally Posted by CD Smalley

Test your fuel pressure. I'd suspect a weak pump first off. TBI must be 9-13psi.

Next would be an ignition module. Get the pressure first before you throw parts at it an further.

Hi Smalley,

Thanks for the reply. The I was going to take a shot at checking the fuel pressure tonight. Is it easiest to check at the fuel filter outlet or throttle body?

Does the ignition module control signal to the injectors?

Thanks

CD Smalley · 08-13-2009, 06:41 PM

With TBI you have to do it inline. Meaning there is an adapter that has to go in place of the fuel filter.

The ignition module would shut off the ignition and as the engine died, everything else.

wolf8963 · 08-13-2009, 10:36 PM

I tried to check my fuel pressure tonight but couldn't. My fuel pressure gauge did not have adaptors that would get my meter inline either at the fuel filter or throttle body.

My car book agrees with Smalley, that the gauge has to go inline (though it says to do it at the throttle body) but the connectors are much larger than the adaptors I have.

I checked at Autozone and their gauges didn't look any better in regards to connector selection - they didn't even have a T-connector.

Is there a special gauge kit or set I have to get for this vehicle? Where can I find it?

There are 2 fuel lines going into the throttle body. Does any one know which is the supply line (right side or left from inside the van) or the relief?

OH for a service port!

Thanks for your help!

Frustrated in Urbana

wolf8963 · 08-15-2009, 07:27 PM

OK,

After chasing all over and getting adaptors so I could connect my fuel pressure meter, I was finally able to check it.

It came it at right at 13psi - so that part looks good.

Any other ideas?

Thanks!

wolf8963 · 08-15-2009, 09:07 PM

Some addititional information:

I hooked up an analog volt meter to one of the injectors hoping to see if the signal to the injector was dropping out.

I expected to see a pulsating voltage across the two injector leads but instead I saw almost no voltage - even when it was running "properly".

So I measured each lead to ground - both running and not.
In both cases I saw 12 V when running. As/after it dies (cant tell which) it drops to about 11.5 then drifts up to 12.5.

At this stage of the game I don't have a clue what to check or try. Any ideas would be quite appreciated.

Thanks!

CD Smalley · 08-16-2009, 07:49 AM

Might be time for that ignition module. Does the van fail when it's hot or cold or does it matter? I mean vehicle temperature, not ambient.

wolf8963 · 08-17-2009, 09:44 AM

sounds worth trying. Would it be worthwhile to hook up the inductive timing light to a couple of the plug wires and see if it fires when the van won't run or just it replace and hope for the best?

It can be stone cold and cut out, or it can be at operating tempurature or even running hot.

When I replaced the regulator diaphram, I disconnected the battery - which of course cleared the codes, but I've run it and it's died many times since then and it's not generated any ses codes.

The AC delco regulator for this model is $70 1yr warranty. The BWD is $40 limited lifetime. I'm mighty tempted to try the BWD since I don't know that this is the problem. I haven't done one in this vehicle before. Is it hard to get to, or the usual right under the distributor cap? If it's easy to get to I will defintely do the BWD and if that's it and it fails again later I'll just do an AC Delco then.

Thanks again
I'm going to kick myself if it's the module and I've been chasing fuel problems all this time.

wolf8963 · 08-18-2009, 12:22 AM

Got home and tried putting a timing light on a plug wire and on the coil wire to see if the ignition module was firing when it wasn't running.

Naturally the van wouldn't cooperate and though it died a few times, it usually started back up too quickly to determine if it was or wasn't firing.

Though it didn't start hard enough to be certain, it seemed as though the ignition was firing the times it started a little hard.

I'll check again tomorrow and maybe it will cooperate by not starting. In the meantime, any other ideas I should check?

Thanks

CD Smalley · 08-18-2009, 05:35 AM

It is under the distributor cap as you suspected.

Old Master what do you think about this one?

wolf8963 · 08-18-2009, 08:10 AM

Hi Smalley,
Thanks for all of your advice thus far.

OK,

I retried the test this morning and it was a little more cooperative - ie hard-starting.

With an inductive timing light on the coil wire, I cranked it and it had trouble starting but the coil was definitely firing. It's possible that it was firing weakly and/or missing part of the time as after it started, the light was more continuous and brighter.

I was hoping for a definite aha moment where I could say "aha, see, the coil isn't firing then suddenly kicks in and it starts: but no such luck.

So if you, or old-master, or anyone has any ideas of what else I can check, I would be Soooooo appreciative. Or if you think I should shot-gun it and try replacing the the ignition module?

Thanks again - I'm completely puzzled. I'd think I'd at least get an engine code that might give us a hint....

clueless

wolf8963 · 08-18-2009, 04:42 PM

Any suggestions on what I can try tonight that might move things forward or eliminate anything?

Smalley? Old_master? or anyone?

Is it at all likely that it is the PCM?

Thx again!

CD Smalley · 08-18-2009, 08:29 PM

It could be the PCM. But I'd wait before spending the $$$ for that. There is a weatherpack connector that connects all of the wires going to the tank for the fuel pump, gauges etc.... I'm not sure which one is the power wire for the tank.... But I'd check that wire at the connecter the next time it dies and won't start.

Frankly I'd really suspect ignition module at this point. But would like to hear what OM says....

wolf8963 · 08-20-2009, 09:16 AM

Any sign of OM?

I'm going to go ahead and try the ignition module tonight unless anyone has any other suggestions....

If OM is out there I'd like to get his opinion first...

thx

PS I've had problems getting in to the board the last 2 days. All day yesterday until late in the evening, and also some today, I'd get the "site under heavy load" when I tried to hit www.automotiveforums.com and I wouldn't even get the image. I snuck in the back way today (came in via a google direct to a thread) but that didn't work yesterday. Is anyone else having trouble?

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