Mechanics

WON'T START GOOD SPARK, GOOD FUEL AND GOOD PCM

1998 Chevrolet Astro • 216 miles

Van ran good and strong, except for some cold mornings it would take two or three times to start and then one cold morning it wouldn't start. It cranked over and sputtered a few times and ran the battery down. I charged the battery later that day and refused to start even with starting fluid. So I checked the fuel pressure and found it at 45 psi and so I replaced the pump. And now the fuel pressure is 60 psi and drops to 56 psi and holds for over 15 mins.
I checked for spark and it was good and checked for injector pulse it’s was good. But it still wouldn’t start so I replaced all the ignition parts including the crankshaft & camshaft sensors nothing worked, no fuses blown, no PTC codes I even get live data on the scanner. I also checked all the voltage pin outs form the pcm to sensors and grounds. When that all checked out ok I went to the distributor and checked timing with #1 at TDC, then did a compression test all checked out good. Then I pulled the distributor and checked for play and gear for damage, it was fine, had some wear. The only thing I can think of is the pcm so I replaced that. I know what you’re thinking CKS or bad wiring connections nope all look real good…. I have replaced three of them thinking I got a bad one…

I was told there has to be a bad ground or broken wire some where but I can't find one, hopefully you can steer me in the right direction.
HELP
Avatar
Ccupdave
February 15, 2012.




Test the fuel pressure


Cadieman
Feb 15, 2012.
Sorry jumped the gun try and spray the intake to see if it cranks


Cadieman
Feb 15, 2012.
Are you sure before you pulled the distribter the rotor was pointing to the#1 wire on the cap? You maybe 180 out and may need to put it in on exhaust stoke.I just hold my finger in the plug hole. Bump the starter until you feel compression then turn it to tdc. Then install the distribter with the rotor pionting to the number 1 wire. Recheck all your work some things not wright.


Cadieman
Feb 15, 2012.
Thanx for the reply Cadieman,
Yes I'm 100% sure; it was very hard just to find TDC. I had to use an inspection mirror and a light to reflect the light. The first time it was 180 out when I had it to TDC so I had to crank it around again I seen the cap design ,
So you know this motor doesn't back fire, it just does the same thing. It will sputter like it wants to start one time then crank and crank, as soon as you let off the key it sputters again and runs backward one or two revolutions. I know that s what its doing because I see it on the live scanner data it showed up as -1 on the scanner. The scanner showed about 165 RPM while cranking the motor.
Remember this ran good, no warning signs except for recirculation s of the key to get the fuel pressure up enough to start it on cold mornings, but the fuel pump has been replaced and works good, hold good pressure even while cranking, over 60 psi on crank. The leak down test was good too, never dropped below 56 psi with new fuel pump even after 30 mins.
RE: Distributor I didn t pull the distributor until the last resort anyway. But systems are the same nothing has changed except when I accidentally crossed two wires and caused a back fire when I put the wires back on.
I have been working on this for a month on and off when I couldn t find anything wrong I put the new flashed PCM in it; I got the VATS back right too.


Tiny
Ccupdave
Feb 16, 2012.
Hemmm. So what happen to this has nothing to do with what I did.
It has to be something that happens to these astros.
It's very hard to go over this wiring as it's a van everything is tight and there are tons of wires on the OBD II system can't wait for the OBD III. LOL
AD


Tiny
Ccupdave
Feb 16, 2012.
This has to be a timing issue. Go to the parts store get a diagram of the cap and where #1 wire gos in the cap and make sure the wire is in the right hole. Then get the firing order and recheck them also.


Cadieman
Feb 16, 2012.
Thanks for hanging with me on this
Yes this is definitely a timing issue I agree but why? The CKS is what sends the timing signal to the PCM, the PCM sends the signal to the ICM, the ICM sends the signal to the coil and the spark is sent to the distributor etc. I know it seems like a possible firing order issue, but how if it was running fine? I didn't change the distributor cap till late in the game well after the fuel pump. This had the timing issue before the cap. It can t hurt to check again I guess, I ve already check most of the ignition system two or three times.

I do have the manual for this; it s a Haynes, not a service manual
From what I ve read I see two PCM system grounds 1, BLK/WHT and 1, TAN/WHT Now I ve check the Black/White ground and it s fine at the PCM but haven t found the other yet. From what I understand the PCM grounds play a major roll here
Is it possible the ground is bad for the ICM and get spark?


Tiny
Ccupdave
Feb 16, 2012.
Ok I just did some more checks today, Re: Firing order that check out fine, the numbers were on the cap too. Re other PCM ground checked out good to the PCM also "the tan/wht stripe" located at thermostat housing. I also took another look at the ICM wires too.
I m back to thinking bad new part CKS; I did do some ohms checks on the old one and three other new ones. All the Crankshaft Sensors read the same, 500 ohms at the signal and ground pins on the sensor off vehicle. The specifications should be 800 to 1200 ohms.


Tiny
Ccupdave
Feb 16, 2012.
Put #1 cylinder on compression stroke tdc then remove the cap is the rotor is pointing to the #1wire on the cap?


Cadieman
Feb 17, 2012.
I did that already and it was lined up right, remember when I pulled the distributor and check it for possible damage it was 180 degrees out 1st time and I had to turn the motor over one more time, this was done before I pulled the distributor out. It was pointing to the right mark on the cap, there is also a mark on the distributor housing with this it makes it almost fool proof. I can take pics. If you want to see, but I'm sure it's right, like the firing order. So you know I seen the cap design and I know how it works it points at about one o clock on #2 for #1 on the distributor at TDC looking from the back of the motor.
It almost has to be a defective new crankshaft sensor I used cheep ebay after market ones. I ordered another one this time it s an AC Delco from Rockauto; Advance AP here doesn t have the AC Delco in stock just the cheep after market one.
Wouldn t you think I should rule this out 1st?


Tiny
Ccupdave
Feb 17, 2012.

AD