91 Astro, 2WD with TBI, still starting hard! Help!

[The Scotsquatch]

Hey guys and gals! Maybe you can help me with this one, cuz it has me stumped!

Our van is a 91, 2WD, with the stock V-6 (217K miles on engine, 4K on rebuilt transmission), and TBI.

When we first got the van, it was running very rough, but it had 6 year old gas in the tank and a blocked cat. It would take 20-30 seconds to start, and would only start with the gas pedal depressed about half way. You would have to hold the gas pedal in for a few minutes while it warmed up, and then it would run, roughly, with hesitations and lag, and a cloud of white water smoke coming out of the exhaust, even though it doesn't loose any coolant...probably from the old gas, since it smelled so bad!

The first thing I did was put all new plugs and wires in it, a new cap and rotor, and found a fried water temp sender wire (the one that goes to the guage on the dash)...and I siphoned out all the old gas and filled the tank with fresh hightest fuel. The dash gauge started working fine, but there was no change in the way it ran or started!

Next I went to the timing. Checking it with the brown wire disconnected, I noticed it was advanced about 3 degrees. I brought the timing back to 0 degrees, and the van would barely run! No power at all, VERY serious lag, and wanted to stall on the test drive every time we stopped at a light or stopsign. So I brought it back to 3 degrees and it ran like it did before.

With the doghouse off and the aircleaner removed, watching the fuel injectors when it would start, it would take about 20 seconds for fuel to even start to dribble from the injectors, and that is exactly what it was doing at idle, just dripping into the TBI, although the fan/cone pattern seemed ok when you gassed it. And the fuel pump was VERY loud, so that was the next thing I did:

I dropped the fuel tank and replaced the pump...and the pickup sock, which was no longer see-through, but varnished dark brown from sitting in that old gas. Back the tank went in, and then a new fuel filter.

The results then? The fuel would still take about 20 seconds to start flowing from the injectors, but this time it actually flowed in a nice cone, and then with the pedal depressed, a nice even strong cone on both sides. It still took 15-20 seconds to start, you had to push the pedal down about half way to get it to start, and let it warm up so it would idle without stalling. There was still some lag driving it, but not nearly as much.

It would still smoke at startup, water vapor smoke for the most part, although the old gas smell was gone. So, I'm thinking the cat must be blocked.

Next I eliminated the cat with a 2 1/4" straight pipe flared to 2 1/2 inches to fit over the head pipe, with a new cylindrical muffler with 2 1/4 inch inlet and outlet, and reused the stock tail pipe, although I had the muffler shop repair the end of it where it plugs into the muffler, and used universal hangers in the stock locations...the result? No more smoke at startup (except a puff of oil smoke when you first start it up...hey, it has 217K miles on it, so its just a little puff from the valve guides), no more lag at all, more power than I thought these things could have, and runs great! EXCEPT....it still starts hard! 15-20 seconds! At least now it will almost start after about 15 seconds without pushing down the pedal, put to actually start it, you have to push the pedal half way down...and you still have to hold it at a higher idle for a minute or so before it will idle without stalling. Once it warms up a little bit, the idle is smooth, and the van runs great. Observing the injectors again, it doesn't get any gas spraying out for that whole 15-20 seconds that it won't start, and then once the gas starts spraying, it starts right up (with the pedal held down a bit)!

So, in summary:

No more cat, a new muffler, fresh gas after flushing the tank, new fuel pump and pickup screen, new fuel filter, new plugs and wires, new cap and rotor, new air filter, and a burnt temp sender wire repaired...

The results?:

It runs awesome now...except it still takes 15-20 seconds to start! And it will only start if you depress the gas pedal about half way! If you turn the key, it will catch and want to fire up after 15-20 seconds, but it won't start without pushing the gas pedal down. And then you have to hold the pedal down for a minute or so to keep the idle higher until it warms up a little, or it will stall. After about a minute or so, you can take your foot off the pedal, and she idles smooth. And it has all sorts of power now! No more lag in acceleration, no more skipping...and I think I have to bring the timing back down to 0 degrees, because now it seems to be idling a bit too high...if you are in gear at a stopsign or light, she wants to keep going! The transmission wants to keep on keeping on, so you have to shift it to neutral at a light or else the whole van vibrates.

That said, any ideas on why she is starting so hard?

The fuel pattern from the injectors on the TBI look great and even on both sides...although again, I did notice that when I start it without the doghouse or air cleaner in place, fuel doesn't shoot out of the injectors right away...it takes 15-20 seconds for the injectors to start spraying, and when they start spraying is when the engine finally starts.

It almost seems to me that something is telling the computer not to supply fuel right away for some reason...does it sound like any sensors you know about? Maybe the computer is getting a false code, telling it that the engine is already warmed up? By the way, she starts right up when the engine is at full warm-up...if you drive it for a while and then shut it down, she'll start right back up...once it cools down again, its hard start time again!

Oh yeah, the fuel pump runs constantly, although the new pump is quiet...is it supposed to run constant, or is it supposed to reach a certain pressure and shut itself off?

My next step is to remove the TBI, take it apart and clean it up, and then reinstall it...but I don't really thing this is the problem, since it looks spotless inside down the throats. I'm still thinking that since the fuel isn't getting delivered for that 10-15 seconds, it has to be one of the sensors...any idea which one/ones would do this?

Help me troubleshoot this please...lol!

Kev

[rlsllc]

Sounds like a bad fuel pump relay to me. Does your pump run for 2 seconds or so as soon as you turn the key to run (without cranking the starter)? It should.

I'd jumper the relay so the pump is running, and then hit the key. It should hit right away. You could also swap the HVAC relay and the fuel pump relay (they're side by side) for a test.

ps, i had a bad ignition module a while back that caused my van not to fire the injectors. It was intermittent at first, hard starts, stalling, then no run. It got progressively worst, until it stranded me a few times. This is the test procedure from V8 Famvan (James):

I would suspect your ignition control module - here is why.

Your ignition control module supplys the signal to the ECM to tell it to fire the injectors. It also supplys the ignition / spark signal. It can fault in the manner you have, as in spark is ok but has no injector drive.

How to test the injector control system.

Connect the aligator clip of a simple test light to a battery source.
Disconnect the larger (4) wire connector to the ignition control module.
Turn the ignition on.
Touch / release the test light tip to the purple/white wire in the 4 wire ignition control module.

What should happen is this:
The fuel pump prime will trigger - 2 seconds.
The injectors will pulse/spray fuel.

If you have no injector pulse/spray when cranking, but do have spark & it passes the above test - you have a faulty ignition control module.

_________________
James from B.C.
1992 Safari
.060 350 V8

Mine ran great when it ran, and stalled and started hard more and more until it became very unreliable.

[The Scotsquatch]

Hmmmm...sounds like it could be the ignition control module...

But, my fuel pump runs constantly...it doesn't shut itself off at all. From the moment you turn the key, the fuel pump is running. Quietly, but it stays running the whole time the engine is running, of for that matter, the whole time the key is on, engine running or no. Is it supposed to reach a certain pressure and then shut itself off? Its a brand new pump I bought at NAPA...could it be faulty, or would the relay be faulty, or already jumped by a previous owner? And if so, would that cause the hard start?

And if its the ignition control module, I can test it with your proceedure...is that the control module that is inside the base of the distributor cap? And is it an expensive part if it is faulty?

And I forgot to mention: We are in Florida right now, with temperatures right now from 60 degrees Farenheit, to 80 degrees Farenheit. A lot of you are in the north right now with freezing temps, so I want to make sure you know the ambient air temp down here to help me troubleshoot this.

Thanks again, and please keep the replies and ideas rolling!

Kev

[The Scotsquatch]

I found something that may be the problem, although I am still leaning towards the ICM. Near the starter, there is a skinny wire that looks like it is supposed to connect to the starter terminals, but is broken off. The starter turns the motor even without this wire connected, but could it be some sort of sensor wire that tells the computer the starter is turning over so it can immediately start the fuel injectors flowing? It seems painfully obvious, but is it possible this one dangling wire is causing my problems? If the wire is supposed to connect to the starter, I'm going to hook it up today and see if that is the problem...I'll look in my Haynes manual and see if it is supposed to be hooked to the starter, and then hook it up to the right terminal. Could this be it? I'll let you know this evening after I hook it up.

Keep the replies and ideas flowing, folks! I know this Astro can be made to start and run like new!

Kev

[kings-x59]

One thing I would check is the fuel pressure. With that much mileage on the TBI system, your fuel pressure regulator is suspect. Check the pressure with the engine running. Then shut it down and check the pressure after it's been sitting a while. After I replaced my fuel pressure regulator, I found that the fuel system would hold operating pressure over night. From your write up it sounds like the system is having difficulty building up to the needed operating pressure. I found the replacement parts for the pressure regulator to be shockingly expensive. I think I paid $45 for the little rebuild kit. If you do replace it, spend another $13 for the Throttle body rebuild kit and clean and rebuild the throttle body while you are at it. You'll have to pull the whole Throttle body and disassemble most of it to get the the regulator anyway.
The TBI systems run on pretty low pressure. I've read that the injectors need a minimum of 12.5 psi to work properly. You'll have to add a fitting between the fuel line and the throttle body to test the pressure. There isn't a schraeder valve on the TBI setup to hook up a pressure tester. In my case, I bought a pressure gage and fitting as a kit. The pressure gage is a permanent resident on my fuel line now. If memory serves, I ordered it from cfm-tech. One last thing on pressure gages, use a low pressure gage. I've had gages designed to read up to 200 psi give me inaccurate readings in the low end of the scale.

[The Scotsquatch]

Well, it wasn't that wire hanging by the starter that was the problem...I'm not even sure what that wire is supposed to go to, but it seems to be a ground maybe? With my Fluke attached to it and a good ground, there is intermittent continuity to ground, key on or off. It is an orange skinny wire for the first 8 inches or so, then it goes to a small white plastic box/fuselike thingy marked with a "20", and then the wire coming out of it is black. It is in the same harness that goes to the starter, and the wire follows all the other wires back up into the engine compartment. Any idea what this wire is? There is a ground terminal on the back of the starter, so I'm thinking it is supposed to be an aux ground wire for the starter maybe?

Anyhow, I temporarily hooked it to the starter ground, and it makes no difference...it is still starting hard.

Fuel pressure regulator might be it, might be the ignition control module, might be any of the very many senders...argggg!...lol! I'm on a budget so I can't go replacing things left and right, so I'm trying to narrow this down. Any more ideas?

My buddy Tom said it might be the oil pressure cutoff switch, located near the distributor. Anyone ever hear of this? He said it tells the computer if the oil pressure is below X psi and the computer won't trigger the injectors unless the oil pressure reaches high enough and the rmps from the starter are at least 400 rpms...ever hear of this being an issue, and is it something I can just jump across to check?

The mystery continues!

Kev

[kings-x59]

The oil pressure switch ( sensor ) might do that, but I'm not holding my breath.
Here's a how to, on how to test it.
http://www.autozone.com/az/cds/en_us/09 ... oPages.htm
When you turn the key, the fuel pump operates for about 2 seconds to pressurize the the system. Until the engine starts, there is no oil pressure. If the fuel pressure is good and the spark to the plugs is good, the engine should at least try to turn over inside of 20 seconds.
Have you checked for stored error codes? I understand that the SES light is not on, but are you certain the bulb is good? Has the SES light come on at any time and then gone out? If so there is a code stored in the pcm.

[The Scotsquatch]

The light does come on when you are trying to start it, and you try too long before it starts...lol. It goes right out once the engine starts. It did come on on me the other day though, on its maiden voyage without a cat...it came on after about 10 minutes, and stayed on till I drove it home, about another half hour of driving. It hasn't come on since, except during starting, and then shuts off when the engine starts.

Kev

[kings-x59]

Well that confirms that the SES light bulb is good. The SES light should come on when you turn the key, and go right back out when the engine starts, so that sounds normal too. The SES light coming on after having removed the CAT is not normal, but is most likely not related to the hard start problem. It's more likely related to the O2 sensor. With the CAT gone, it' probably not heating up sufficiently within the specified time period.
The PCM will store multiple error codes however. You can pull the error codes by jumping the A and B terminals on the ALDL with a straightened out paper clip.

[The Scotsquatch]

I changed the oil today to Castrol 10-W40, put in Slick 50, changed the filter (Fram), and changed the oil pressure sending unit...and voila! It ALMOST starts right up!...lol

If I turn the key to ON without trying to start it until the seatbelt light goes off (the pump runs in the background) and then turn it to start for 3 seconds, turn it back to on, and then back to start, it fires right up, without giving it any gas, and idles smoothly.

If I skip the double key turning, it takes about 5-7 seconds of holding the key on start, and then she'll fire right up without giving it any gas.

Hey, its a major improvement! Still not perfect, but getting better!

Kev

[The Scotsquatch]

All of the work I did so far didn't entirely solve the problem: The Astro starts now in 5-10 seconds instead of 30...So my guess is the fuel pressure regulator...it doesn't seem to be holding fuel pressure when you shut it down, and acts like you are repriming the lines when starting it up. Guess I'll have to pull the TBI, clean and rebuild it, replace the fuel pressure regulator, and then replace all the electronics like the TPS before putting back in the TBI...I'll let you know how it goes!

Kev

[kings-x59]

Rebuilding the TBI isn't a bad job. A single edged razor blade is handy for removing the various gaskets.
You may find some serious carbon build up at the pcv hose port.