1997 Chevy S-10 Hard Starting with Stall. Oil Pressure Swit

Tiny
NTL1991
  • MEMBER
  • 1997 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 172,000 MILES
Here's my problem. The engine cranks for about 5 seconds, then either dies or starts very rough and stalls. Immediately after, when cranking for a second time, the engine starts perfectly after 1-2 seconds with a good idle. Could the Oil Pressure switch that cuts power to the fuel pump when the pressure is too low be the culprit? If I keep cranking to get the pressure up, it stalls, and then immediately after crank again and the pressure is high enough, it'll start. It ALWAYS starts on the second start. Is there a bypass to the sensor when the starter is engaged?
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Monday, September 29th, 2008 AT 2:46 PM

16 Replies

Tiny
JACK42
  • MEMBER
More likely you have a blown fuel pressure regulator that is dumping raw fuel into the engine causing the misfire and the lack of fuel pressure on initial start up. If you remove the upper intake (plastic cover) the reg is on the pass side, if it is gas washed under it, the reg is bad.
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Monday, September 29th, 2008 AT 3:34 PM
Tiny
NTL1991
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Well, the truck is only getting about 10 mpg as it is, might that also point to a blown fuel pressure reg? By the way, the engine is brand new (reman) with only 2500 miles on it. The intake manifold is new, also.

Thanks,
Nick
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Monday, September 29th, 2008 AT 3:46 PM
Tiny
JACK42
  • MEMBER
That again points to the regulator being blown.I would check it out so you dont wind up gas-washing the cylinders and hurting your new engine
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Monday, September 29th, 2008 AT 3:53 PM
Tiny
NTL1991
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I do have a fuel pressure tester, are there any tests I could run before I go in and take the intake manifold off?

Thanks
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Monday, September 29th, 2008 AT 3:56 PM
Tiny
JACK42
  • MEMBER
If the fuel pressure doesnt jump up when the engine is reved, the reg is bad.
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Monday, September 29th, 2008 AT 4:03 PM
Tiny
NTL1991
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It jumps up to about 65-68 psi from an idle psi of about 57. The pressure is also stable when the engine is turned off, no drops, etc.

The engine revs perfectly even up to Redline without a miss or anything.
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Monday, September 29th, 2008 AT 4:25 PM
Tiny
JACK42
  • MEMBER
Could be an injector bleeding down over time. Leave the gauge on it to see what hapens to the pressure. Might even be a bad oring in the fuel/injector block in the intake
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Monday, September 29th, 2008 AT 4:42 PM
Tiny
NTL1991
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After shutting the engine off with a fuel pressure reading of about 61 PSI, 5 to 10 minutes later, the pressure is down to about 45 PSI.

Does this signal a leaky injector? What's my next step?

Thanks,
Nick
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Wednesday, October 1st, 2008 AT 2:34 PM
Tiny
JACK42
  • MEMBER
Still might be a leaky regulator.I have actually pulled out the injector nozzles and rested them on dry rags to see if any of them were leaking down.
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Wednesday, October 1st, 2008 AT 3:32 PM
Tiny
NTL1991
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After about 10 hours of sitting cold, I checked the pressure and it's reading 0 PSI.
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Wednesday, October 1st, 2008 AT 8:27 PM
Tiny
JACK42
  • MEMBER
That is why it is hard starting, no fuel pressure, it has to build it back up and the lines have air in them before it can start
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Wednesday, October 1st, 2008 AT 8:51 PM
Tiny
NTL1991
  • MEMBER
I have some more information that might be of some more assistance.

I noticed that the engine will have a severe misfire (strong enough to flash the MIL and set the P0300 code), but only in 2nd gear. If I'm going 35 miles an hour in 2nd gear (about 2500RPM) and I try to coast or maintain a certain RPM above 2000 and lightly have the accelerator pressed, the misfires happen. When I accelerate in 2nd, nothing. This problem doesn't happen in Over Drive. When I stop in 2nd, nothing.

The engine was also at operating temperature, but it will also do it when it's cold.

The first time I tried to recreate the conditions and set the P0300 code, it also set P0147 and P1351 along with it. The second which I let it misfire only for a short period of time, set only the P0300.
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Friday, October 17th, 2008 AT 10:24 PM
Tiny
JACK42
  • MEMBER
P0147- o2 heater circuit
P1351 - ignition control circuit high voltage
Both of these could be related to a faulty PCM or bad wiring/connections. Test to see if you have 12 volts at the o2 sensor for the heater circuit. If so, the sensor may be bad, but the other code requires alot more diagnostic. Have you signed up for our online manual (Mitchell) to use as a diagnostic aid?
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Sunday, October 19th, 2008 AT 8:45 AM
Tiny
NTL1991
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No, I have AllData.

I have a question though. The engine that came in my truck was an X-Vin 4.3L V6. When that engine threw a rod, it was replaced with a long-block W-Vin 4.3L V6 engine. The PCM is original from the X-Vin. Are the PCMs the same from VIN to VIN?

Nick
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Sunday, October 19th, 2008 AT 2:48 PM
Tiny
JACK42
  • MEMBER
The original was an X or Z? Z is throttle body. The PCM wont matter, you didnt change the fuel injection, only the engine under it
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Monday, October 20th, 2008 AT 9:41 AM
Tiny
NTL1991
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The original was an X-Vin engine.

I did notice today that the misfire also occurs much more frequently when the truck is cold. Even in park, the engine would misfire repeatedly when revved and even when under full throttle. This disappears when the truck warms up.

Nick
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Monday, October 20th, 2008 AT 1:14 PM

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