Almost starts

Tiny
SONOMA BEACH
  • MEMBER
  • 2000 GMC SONOMA
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 216,000 MILES
When starting, after I hear the engine fire and begin to start up it shuts off after releasing the key switch from start cycle to run cycle. This has happened twice in the last 6 months. After it sets for some time - 30 to 45 minutes (and having attempted several times to start again without success) it will go ahead and start as if nothing happened. Acts like no fire when malfunctioning but cannot confirm as yet.
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Tuesday, April 19th, 2022 AT 2:18 PM

17 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The ignition control module (ICM) receives a signal from the PCM to trigger the correct coils. Since the PCM controls spark timing and ignition control during crank and run, there is no bypass mode. Therefore, if you have spark in the start position (it starts) and lose spark in the run position (stalls), chances are the ICM is going bad.

The ICM is what the ignition coils mount to. You can remove it, and have it checked, but if it isn't happening at all times, it may produce a false positive.

If you look below, I added the directions for replacement. You may want to consider removing and inspecting connections.

Let me know if this helps or if you have questions.

Take care,

Joe
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Tuesday, April 19th, 2022 AT 8:39 PM
Tiny
SONOMA BEACH
  • MEMBER
Many thanks for the help. I will try suggested repair and have ordered suspected defective part in case the connections and other components check out okay.
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Thursday, June 2nd, 2022 AT 9:07 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

You are very welcome. Don't quote me, but I believe places like AutoZone can test the one you have. That way we can be certain.

It's just a thought. I don't want to take the chance of wasting anyone's money considering it just cost me 100.00 to fill my tank. Ugh! Things have sure changed.

If possible, let me know how things turn out for you.

Take care,

Joe
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Friday, June 3rd, 2022 AT 6:58 PM
Tiny
SONOMA BEACH
  • MEMBER
Joe finally got the opportunity to replace the suspect part - ignition module. Started right off, I'm jazzed. Hope this is the cure since there can be so many other causes for difficulty starting. Thank you so very much for your help!
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Saturday, July 30th, 2022 AT 6:12 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

Thank you for the update and you are very welcome. I'm glad to know it's working again.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe
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Saturday, July 30th, 2022 AT 8:28 PM
Tiny
SONOMA BEACH
  • MEMBER
Well shoot, I spoke too soon, I guess. When it fired right up after module repair, I was certain that was the fix. After it set overnight and getting ready to leave for work today - same thing again. Crank, crank, and more crank, no start. I got it started finally this afternoon. I'm thinking I'm losing fuel pressure after sitting for an extended period. Once it did start, it would still start up right off after letting it sit for 10-15 minutes. Sound like a pressure scenario, or pump not working correctly? It runs so it must be working to some reasonable amount but maybe not enough to maintain system pressure?
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Sunday, July 31st, 2022 AT 6:18 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

It does sound like fuel pressure drop-off. First, here is a link that explains in general how to test fuel pressure. You will need a fuel pressure gauge, but most parts stores will lend one to you.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

However, I want you to try something that will let us know if fuel pressure is dropping off.

Try this:

1) Turn the key from off to the run position (engine off) and count to 5.

2) Turn the key back to off and repeat step 1 a total of 5 times.

3) On the 6th time, see if it starts normally.

Let me know what happens.

Take care,

Joe
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Sunday, July 31st, 2022 AT 10:09 PM
Tiny
SONOMA BEACH
  • MEMBER
Joe, I was able to try the 5x key switch method today. When starting (6th try) it fired briefly then cranked for about 10 seconds before firing in a chug-chug-chug manner and then starting. ( Try to imagine Humphrey Bogart kicking the boiler on the African Queen to get it going) kind of like that - sort of. But it did start and idle normally afterward and I let it run for a few minutes to see if it might kick a "check engine code" but nothing showed. I shut down and waited a few minutes and tried again - started as if nothing was wrong. I checked my fuel rail and there is no service port for testing fuel pressure. My Chilton's svc. Manual says to make a tee fitting using fuel lines and connect to fuel line(s) before the filter to test fuel pressure. Thanks for your input on this - i'm getting a baptism by fire (not literally, I hope) in troubleshooting this problem. The book has some specifics on it but it seems to be more detailed on the 6 cyl. Engine and I'm working on the 4 cyl 2.2l.
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Tuesday, August 2nd, 2022 AT 6:17 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Check the fuel pressure regulator on the fuel rail. It will have a vacuum hose to it. Remove the vacuum hose and see if there is any evidence of fuel in it. If there isn't, start the engine and confirm there is a vacuum to the hose.

If there is, the only other way to test the regulator is with a vacuum pump to see if it holds a vacuum.

Let me know.

Joe

See pic below.
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Tuesday, August 2nd, 2022 AT 10:47 PM
Tiny
SONOMA BEACH
  • MEMBER
Was finally able to find the test port at end of fuel rail. Checked 45 PSI with key "on"- up to 57 PSI when running. Obd2 showed two codes - P140/P143 bank 1 sensor 1 (upstream)- replaced both up and downstream sensors. Same symptoms exist - extended cranking time to finally start and noticeable odor of gas thereafter. Once running, seems fine. Am leaning toward possible injector malfunction/leak. Have you ever encountered this problem before?
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Wednesday, September 14th, 2022 AT 8:07 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I attached the fuel pressure specifications below for your review. See pic below. The pressure you indicated doesn't sound right. With the key on and engine off, it should be between 56 and 62 PSI. The fuel pressure should drop approximately 5 PSI with the engine started.

Here is what I need to know: When testing pressure showed approximately 50 PSI, how quickly did it start to drop when the key was turned off? If it dropped quickly, chances are there is a leaking injector.

If the pressure drops more than 5 PSI in a minute, we need to further test the pressure. It will require a fuel pipe shut-off adapter. It's GM part number J37287 if you want to look it up to see what I'm referring to. This step tests for a loss of fuel pressure between the shut-off adapter on the fuel feed pipe and the fuel pump. If there is no loss, then you have either a leaking injector, fuel pressure regulator, or there is a leak somewhere between the fuel rail and tank via the return line.

Let me know.

Joe

See pic below.
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Wednesday, September 14th, 2022 AT 8:39 PM
Tiny
SONOMA BEACH
  • MEMBER
Rechecked fuel pressure today. Key on @ 50psi. Held for a moment and began to drop about 1 psi every 10 secs. Key off- purged pressure and rechecked - 48 psi, held that for a moment and began to drop at about same rate as before. Seemed to hold steady around 40 psi or so. Started and reading was 61 psi. And held during entire run sequence( 3-4 min.). Shut off and dropped slowly about 1-2 psi every 10-15 seconds and held at around 45. I was unable to hear fuel pump running during key on mode due to the chimes going off every time the key is switched "on". Once they quit, I did not hear that familiar "hum" of the pump. Does it cycle to a certain pressure and then pause until pressure is needed again(as in starting sequence?). It must be functioning or the truck would not start and/or run. But, functioning to it's proper specification - that I am uncertain of. Unable to find shut-off adapter as yet and any one listed online is kind of high priced for me at the moment. There is no pressure regulator on the fuel rail - only the bleed off/check gauge valve at end of rail and the 4 ports for the injectors ( which I replaced last weekend). My understanding - not confirmed though - is that the fuel pump has the regulator built in to the mechanism on this model. I last changed the fuel pump about 7-8 yrs previous after it failed completely - no start at all - and after that repair until recently, it has worked without fail. Sorry for the long-winded description but wanted to be certain I included all available info for you to work with. I will keep checking for that shut-off adapter, but I'm hoping it isn't needed. The truck does start, it just cranks longer than usual before it fires up. 5-10 secs as opposed to 1-2 secs. Previously.
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Monday, October 3rd, 2022 AT 6:37 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I suspect the fuel pressure drop-off is the cause of the delayed start. Also, the fuel pressure regulator should be on the fuel rail. See pic 1 below. Is that what you are seeing?

Joe
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Monday, October 3rd, 2022 AT 8:52 PM
Tiny
SONOMA BEACH
  • MEMBER
No, it's configuration is similar, but the relief/test port is at the rear of the rail past #4 injector. - Not on the bend leading back to and ahead of the injector ports #1 through 4 respectively. There is no press. Reg. Fitting or bracket to mount upon on the rail. Per the graphic you provided, the bend being the incoming end/fuel inlet, goes back to injector(s) #1, 2, 3, 4 and then the test port past injector #4. That is where the rail ends. Remove items 1, 2, 3, and the mounting bracket. Items 6 and 7, the Schrader valve, cap and port are at end past injector #4. The injectors I replaced were Delphi brand, not AC/Delco which I installed. I know Delphi has some affiliation with GM, but it seems unlikely that they were not original equipment. And I suspect they weren't the cause but I changed anyway to eliminate them as a possible failure scenario later--since truck is at 210,000 miles. Btw just wanted to say thanks again for your time on this, it is appreciated, as vexing as this problem is/has been. Is it possible GM had 2 (or more?) Different designs for this system? I saw a YouTube video after doing a search for "2000 GMC Sonoma 2.2l flex fuel rail repair" or something similar to that, and the guy in the video had an identical set up as mine. Used his video as reference for r&r of my rail.
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Tuesday, October 4th, 2022 AT 8:32 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I didn't realize it was a flex-fuel vehicle. These have a fuel pressure sensor located on the top of the fuel pump module. See pressure specs below.

The idea that you have flex-fuel is likely why the design is different.

Joe
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Wednesday, October 5th, 2022 AT 4:57 PM
Tiny
SONOMA BEACH
  • MEMBER
Sorry about that. I guess I did not specify that in my previous posts (f/f system). So, likely the pressure drops off sounds like a pending or potential pump failure. One of those symptoms that won't be as apparent until complete failure - at which time it should be obvious. So, I'll start shopping fuel pumps to be prepared for the possible/inevitable likelihood of pump failure. FYI - after the previous pump replacement years back, I tried to think ahead, and cut an access panel in truck bed and riveted a hinge onto cut out panel for "easier" access if needed. So at least in the event of replacement, won't need to drop tank or lift up bed. Hopefully, unless some new developments occur, this should close our dialogue with regard to hesitant start symptoms - if you come across others with like problems let me know if they used different techniques to solve their problems or use my methods as reference - as unorthodox as they may have been. Thank you for all your help and God bless.
Ps. I found that you tube vid and the guy doing it went under the monicker of Lost Socket Motorsports. The video in question referred to "fuel injector change on 2003 S10, fixing a hard start".
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Wednesday, October 5th, 2022 AT 6:09 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

If things change, let me know what I can do to help. Also, keep in mind that fuel pressure drop-off can be the result of a leaking fuel injector or a leak at any point between the tank and the fuel rail.

You take good care of yourself and please feel free to come back any time in the future. You are always welcome here.

Joe
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Wednesday, October 5th, 2022 AT 7:03 PM

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