1997 Chevy Suburban Cranks but won't start--sometimes

Tiny
ANOTHERVIEW
  • MEMBER
  • 1997 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 174,000 MILES
Reference, same car as: http://www.2carpros.com/forum/here-vp58298.html That problem was fixed thanks to your help--thank you.

Since approximately March 2008 we noticed another problem which I describe as: Car cranks but won't start. After releasing the key it does a sputtering or diesel thing and sometimes some backfiring. For months it was occasional, but then no problem at all. Our guess as to why is humidity. When the weather would be very dry, then no problem.

First thing we tried was replacing the ignition switch thinking when in the start position ignition was not really happening. No improvement.

It was hard to troubleshoot because it seldom did the problem, but then a few weeks ago it went bad long enough to test some things. Fuel pressure was good, and spark (with tester) seemed good, but still no start. Chemtool down the air intake no help.

This time there was no starting it even trying for days. We noticed unplugging the MAF and air intake sensors did not produce any trouble codes, so replaced computer on August 28. Now it starts, but rough. Runs pretty well with MAF unplugged, so replaced MAF on Labor day, September 1. Then very happy with the operation of vehicle.

Drove several times, but not every day. September 9 went out in the drizzling rain to start it, but it was back to the original (see above) symptoms.

We have access to a good scanner for getting trouble codes.

Help appreciated.

If you have any questions to help troubleshoot, please send them.
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Wednesday, September 10th, 2008 AT 10:29 PM

18 Replies

Tiny
MASTERTECHTIM
  • MEMBER
Since you have spark and fuel pressure the first thing that comes to mind is a faulty crankshaft position sensor, its located on the front on engine down low by the harmonic balancer, there is actually a gm bulletin for these sensore casuing the timing to go full advance causing your symptom. Use a ac delco sensor and get back to us if this does not fix problem. **This wont necessarily set a trouble code either.
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Thursday, September 11th, 2008 AT 5:44 AM
Tiny
MASTERTECHTIM
  • MEMBER
I dont want to overstate the obvious but you already checked the cap and rotor and coil wire? Just making sure
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Thursday, September 11th, 2008 AT 5:45 AM
Tiny
ANOTHERVIEW
  • MEMBER
We have done nothing to the car all week except try to start it. Tried Tuesday morning and throughout the day. Also on Wednesday and Thursday. All three of those days were raining or very humid.

Today was dry. We tried starting it early morning with no success; midday with no success; early evening with no success. Then tried around 10:00 p.M. And it started right up.

This seems to support our belief that it is related to humidity.

We bought the cap and rotor, but have not installed.

After it started we tried spritzing several things under the hood then starting the engine after each. Every time it started right up. The spritzed (with water) items included distributor, computer, MAF, and at least close to the harmonic balancer.

Maybe that helps?

?

By the way, it is supposed to be very rainy tomorrow.
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Friday, September 12th, 2008 AT 11:49 PM
Tiny
ANOTHERVIEW
  • MEMBER
The humid air started coming over night and it started raining about an hour ago.

I went outside to start the Suburban.

Back to not working---starter cranks it, but no indication of starting.
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Saturday, September 13th, 2008 AT 8:46 AM
Tiny
ANOTHERVIEW
  • MEMBER
Today was a dry day (unfortunately we did not get enough rain yesterday for the plants and pond), and the engine started right up.

After that we replaced the distributor cap and rotor. We thought we had replaced them 18 months/15k miles ago, but based on the arcing patterns, now we think we didn't.

No rain in the forecast so it could be a long time before we know if it is fixed.
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Sunday, September 14th, 2008 AT 5:29 PM
Tiny
MASTERTECHTIM
  • MEMBER
Keep us posted
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Monday, September 15th, 2008 AT 6:11 AM
Tiny
ANOTHERVIEW
  • MEMBER
We were surprised this morning.

Dry day--at least it seemed to us.

Around 7:15 tried to start.
Attempt 1: Turned key, cranked, but no indication of starting.
Attempt 2: Pressed pedal to floor then release, then moved key to start. Cranked and sounded like it would start, but didn't.
Attempt 3: Pumped pedal while key in start. Engine started. I left in high rpm for a few seconds, then foot off pedal; engine died.
Attempt 4: Started again same way, but left in high rpm for about half a minute, then slowly let down to 1k rpm. Idled fine, then let run until wife drove 30 min to her appt.

Leaving appt an hour after arriving: started fine, but died when put in reverse. After that ran fine.

I am thinking maybe replace the coil and ignition module?

PS: Wife insists I mention that when she was driving home volt meter was wavering around the 14v mark with variation +- 1volt. I think this is completely unrelated to the starting issues, but I put it becuase she wanted me to:)
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Monday, September 15th, 2008 AT 6:16 PM
Tiny
MASTERTECHTIM
  • MEMBER
Sorry I have been away for a while but have you tried replacing crankshaft sensor yet? I have seen a numerous number of times that the timing gets advanced and causes it to try to start but timing is too far advanced it wont. Also another one of my fellow techs has also reminded me of the problem of being a faulty fuel injector or injectors. Especially when you stated you hac=d to floor it to start it. They actually redesigned the entire injection system so you have to replace all of them at the same time. I also have had to replace these many many times. A injector bal;ance test or bleed down test will verify. And where the injectors are is the fuel pressure regulator which is also common to leak causing it to flood when cooling down.
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Monday, September 22nd, 2008 AT 1:57 PM
Tiny
ANOTHERVIEW
  • MEMBER
Have not had any problems that I can say are related. Did have some cranking problems, but cleaning battery connections fixed that. I deem unrelated.

Because the weather has been dry, we don't know if the cap and rotor already fixed it.

Regarding your technical comments:

*We have not done the CPS or anything else because we have not had a lot of time, and we don't want to spend any more money until the weather gets more humid to see if it is already fixed.
*I would like to understand more how the CPS can break the timing. Everything I have read says that if it is broken there will be no spark.
*Regarding the fuel pressure regulator, you can see from the link at the top my history on that. I had the exact problem you described about 10k miles ago and we replaced it.
*About the injectors, I am intrigued about that being the problem. Next time we have the problem I should get it tested somehow.

Thanks.
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Sunday, September 28th, 2008 AT 4:56 PM
Tiny
MASTERTECHTIM
  • MEMBER
The faulty cpa advances the ignition timing causing the problem and it's very intermittent. I have seen it cause starters to snap
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Monday, September 29th, 2008 AT 6:30 PM
Tiny
DTMMIL
  • MEMBER
I am having a similar problem with my 97 suburban. It cranks over but won't start right away. Once it starts it will run fine. But the timing thing is getting me thinking. Sometimes after it cranks over it will buck like the timing is off. Can you give me more information on the bulletin about the crankshaft sensor. Mine has about 5000 miles on the plugs, new cap an rotor, newer MSD wires and an MSD 6AL ignition. Any help would be great! Also it sat most of the summer as I ride motorcycle, now I need the suburban and I am pretty sure it won't start when it gets bitter cold out.
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Monday, November 17th, 2008 AT 5:58 PM
Tiny
MASTERTECHTIM
  • MEMBER
More common is for your extended crank is a weak fuel pump. To test fuel pump you need to hook up a amp meter in series from positive battery terminal to test lead for fuel pump which is a single red wire near fuse box under hood. It should have atleast 9 amps minimum, gm has found that if it has less than 9 amps then there is not enough fuel volume to open the injector poppet nozzles causing extended crank. The crank sensor problem is quite noticable as when you attempt to start truck it will seem like timing is severely advanced and have a hard time cranking over.
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Tuesday, November 18th, 2008 AT 5:50 AM
Tiny
DTMMIL
  • MEMBER
Well I got myself a pressure gauge to check my fuel pressure. I hit the key and it jumps to 55psi, turns over for a while, starts and runs at 55psi. I shut it off and left the gauge hooked up and within about 10 minutes it dropped to about 40, 1.5 hours later it is at 30. I am assuming my check valve in the pump is bad and I need to replace the pump.
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Saturday, November 22nd, 2008 AT 5:32 PM
Tiny
DTMMIL
  • MEMBER
Ok, so I left my gauge connected over night, expecting it to show zero this morning. It was back up to 50. I am assuming that the temp dropped or the motor cooled off and the pressure dropped to 30 last night, then this AM it was warmer again so it went back up. I hit the key, it jumped to 55psi and cranked and cranked. I could hear the battery starting to get lower before it finally started. This is really P#$sing me off. I am thinking I am going to put in the 4th set of plugs in the last 30,000 miles and try that.
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Sunday, November 23rd, 2008 AT 8:29 PM
Tiny
MASTERTECHTIM
  • MEMBER
Just because you have 55 psi of fuel pressure does not mean you have enough volume. You need to perform the amp draw test. It will take 2 minutes to do and you will know for a fact if the fuel pump is good. ***This is a commonly known problem with this fuel system and unless you do a amp draw test you are wasting your time.
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Monday, November 24th, 2008 AT 6:35 AM
Tiny
MILT1234
  • MEMBER
I have a 97 suburban also with 194000 miles and it has the same problem. When the humidity is high it wont start. I replaced the distributor cap, I did a tune up on it last summer and replaced the fuel filter in December 2008.
I tried starting it on 04/28 and 04/29/09 after a rainy night with no luck. Both days I had put it in the garage and all I had to do was put a blow dryer on high and set it where the air blew over the distributor cap or about 30 minutes. It started right up. Comeone suggested the coil might have a hairline crack and the moisture is causing it to short out, Going to replace the coil on 04/30.
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Wednesday, April 29th, 2009 AT 10:41 PM
Tiny
MOTO250CR
  • MEMBER
I have a 99 Suburban that has been doing the same thing for the past year. I finally fixed it and I hope other people see this and save themselves some grief. I replaced the cap, rotor, wires, ignition module, coil, crank position sensor, unplugged every plug I could find and put dielectric grease in them. Nothing worked. I finally read on one of these forums to replace the cap and rotor with a GM part. Having already replaced the cap, twice, with an AutoZone cap, I did not see how this was going to make any difference. The cap always looked dry when it wouldn't crank and I looked inside it. So I got a GM cap and rotor last week. It has rained three times, hard, since then and after sitting over night, it has cranked up every time. One note. You have to really crank on those screws to make the cap tight on the distributor. They will get to a point where they feel tight, but the cap will still move around. The cap should not move at all when you finish cranking on the screws. Just don't break the cap. I even put a little silicone where the plug comes into the distributor for good measure. These thing are obviously VERY sensitive to moisture and need a super tight seal. Good luck!
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+3
Thursday, December 15th, 2011 AT 5:46 PM
Tiny
HMAC300
  • EXPERT
If you have athe csi system your pressure should be 60-66 on the fuel pump not 55. If you have the sfi then it shoudl be 56-62 psi. If you have a 350 or 305 it's a 60-66 range. If you have the big block then you have the 56 lb one. Also check your coil wire for corrosion and resistance, it could be bad. One other thing some of tehse late 90 trucks had a fuel pump issue that eh harness near the tank was bad and the cure is to replace the pump with a new connector and about a foot of wire that should come with the pump. This causes an intermittent problem like you are haveing. Also check the resistnce of the crank an dcam sensors, they can have to high a resistance and create problems like you are having and not set a code.
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Thursday, December 15th, 2011 AT 8:09 PM

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