1997 S-10 4.3 4X4 Starting Problems

[Pubdraft]

I have been having a problems with my 1997 S-10 4.3 for the past year or so. When I try to start it it just cranks and cranks but will not start. I replaced the battery when I first started having this problem and that seems to help. I also replaced the altenator 2 months ago. When I get it started it runns smooth and strong. I had the charging system checked out and everything was fine. Also, everytime it will not start I can connect another car to it (like jump starting it) it starts right up.

[BlazerLT]

How about a tuneup?

[Pubdraft]

I have done all the usual tune-up items minus the spark plugs. It only has 55K on it and the plugs should be good for 100k or so. Just today I cleaned the throttle body and when I was done it started right up. I am not sure if it was from the cleaning or the methyl alcohol in the cleaner. There was only some carbon build-up. Also, after it started the "Service Engine Soon" light came on. I let it run for a while and then shut it off and when I started it up again the light was off. BlazerLT, how do you like the Ravin exhaust. Notice any performance increase?

[BlazerLT]

It is a good system.

More performance in the top end.

[J-Ri]

Check the fuel pressure. I bet the pump isn't putting out quite enough pressure with the starter drawing so much current.

[BlazerLT]

Originally Posted by Pubdraft

I have done all the usual tune-up items minus the spark plugs. It only has 55K on it and the plugs should be good for 100k or so. Just today I cleaned the throttle body and when I was done it started right up. I am not sure if it was from the cleaning or the methyl alcohol in the cleaner. There was only some carbon build-up. Also, after it started the "Service Engine Soon" light came on. I let it run for a while and then shut it off and when I started it up again the light was off. BlazerLT, how do you like the Ravin exhaust. Notice any performance increase?

Get the codes checked at Autozone.

If it was on, there was a code stored.

[blazee]

You need to check your fuel pressure with the key on and the engine not running. It should be a minimum of 55-61 psi (it should be more for trouble free operation).

Read this it is taken from an article about CSFI:

From a service standpoint, however, this system has its weaknesses. There are two problems that have ended up being pattern failures. First, the system runs at higher fuel pressure than what we are accustomed to seeing, 56-64 psi. The poppet injectors will not open reliably with much less than 54 psi. I believe it was the Vortec cold hard start problem that was the inspiration for the concept of checking fuel pump rpm by means of the low current probe and the lab scope. The problem occurs during cold mornings when battery voltage is not what it might be. During cranking, voltage to the fuel pump drops. The rpm and consequently the pressure of the pump goes below the level necessary to open the poppet valves. Some of these hard starters took months to diagnose because a tow truck driver would hook up his jumper, and voltage would rise high enough to gain the extra two or three pounds of fuel pressure. Or, the vehicle would be towed in during the cold morning, but by the time the shop got around to checking the vehicle, the ambient temperature had warmed enough to kick up battery voltage, and the thing would start. Techs who were in the habit of not looking stuff up would see over 50 psi on their gauges, and, of course, that had to be enough! Sharp guys like Jeff Bach (current probe guru) and Jim Linder (the injector guru) learned how to scope the fuel pump waveform with the lab scope and calculate pump condition and rpm, almost to the point of being able to predict what day of the year the vehicle would fail to start!

[BlazerLT]

Blazee:

You are slightly mistaken.

For a CSFI it requires 61-66psi to start.

The CPI needs 55-61 but he does not have that motor.

Just a clarification.

[blazee]

Originally Posted by BlazerLT

Blazee:

You are slightly mistaken.

For a CSFI it requires 61-66psi to start.

The CPI needs 55-61 but he does not have that motor.

Just a clarification.

Not according to my Haynes Manual:

Key on, not running:

TBI 9-13psi
MFI 41-47psi
CMFI 58-64psi
CSFI 55-61psi

All should drop 3-10 psi while running.

[J-Ri]

So if the TBI were running within specs at 9 PSI, and it dropped the acceptable 10 PSI with the engine running, it will run with -1 PSI?

hehe, just kidding, but those manuals can be off. The acceptable specs change as problems are found, and obviosly if the manual is printed before the change it can't be updated with the new specs. I'm sure the problem is the fuel pump delivering insufficient pressure due to a voltage drop when cranking.

[blazee]

Yeah,
I'm sure BlazerLT probably got his info from Chilton.
I got mine from Haynes.
And if you notice the guy who wrote the article that I posted has different specs, too.

[BlazerLT]

Yes, I got it from chilton's and this has been referenced with the GM service manual.

It is 61-66psi.

[blazee]

From what I have read in other posts the GM shop manual says 55-61psi as well.


You put way too much trust in that Chilton book.

[BlazerLT]

Where are you getting you fuel pressure reading from?

How can you say mine is wrong?

It has been widely known in this forum that CSFI pressure has been 61-66psi.

[blazee]

There are several sources that all say something different. I'm not saying you're wrong I'm just saying that you shouldn't be so sure you are right. I tend to believe that the 55-61psi is correct for CSFI, because it is in both the Haynes manual and the GM shop manual.