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88 GMC S15 2.5L TBI won't start after replacing head gasket


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bigelow
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Jul 17, 2012, 3:39 PM

Post #1 of 11 (1335 views)
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88 GMC S15 2.5L TBI won't start after replacing head gasket Sign In

Just replaced a blown head gasket in my 88 GMC S15. It's a 2.5L TBI engine. Got everything back together. As far as I can tell I got all of the wiring reconnected. Engine cranks but will not fire. Truck started fine before I tore it down. When I look into the throttle body and move the accelerator cable I do not see any gas squirting into it. However, I don't really know anything about throttle body's so I don't know if they do that like carburators do. Any suggestions would be greatly appreciated.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 17, 2012, 3:52 PM

Post #2 of 11 (1319 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

No, you wont see fuel squirt just looking down throttle body like a carb. Ran before and not now so look for anything disturbed or wrong with the job at a glance and then the basics of fuel pressure, pulse to injectors, spark with a tester and if that shows fine compression if you somehow have this way off by valve timing,

T
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Long retired now


bigelow
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Jul 17, 2012, 4:01 PM

Post #3 of 11 (1313 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

Thanks for the reply, Tom. Can you elaborate on what you mean in regards to checking pulse to injectors? I'm an old carburator guy. Haven't moved up to the injector world, yet. Frown

Thanks.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 17, 2012, 5:23 PM

Post #4 of 11 (1279 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

Noid light is a special and relatively cheap tool to check pulse for injectors. That or just spray some starting fluid or carb cleaner down throttle body if you know there's spark and if it fires up for a second or two then you know it's a fuel problem to chase and can pretty much forget spark problems,

T
_________________________________________
Long retired now


bigelow
Novice

Jul 17, 2012, 5:34 PM

Post #5 of 11 (1275 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

Ok, thanks!


re-tired
Veteran / Moderator
re-tired profile image

Jul 17, 2012, 9:48 PM

Post #6 of 11 (1248 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

If it turns out you have inj pulse and spark at the end of the plug wires, make sure you have fuel pressure. All this stuff checks out , did you have the head resurfaced ? Did you adjust the vaves properly?


LIFE'S SHORT GO FISH


bigelow
Novice

Jul 17, 2012, 10:10 PM

Post #7 of 11 (1242 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

At this point there is no spark at the coil or the plugs. Unfortunately, I ran out of daylight and had to stop for the night. Will start back on it in the morning and try to determine why.


bigelow
Novice

Jul 18, 2012, 11:22 AM

Post #8 of 11 (1214 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

Any recommendation on what to check first to try and determine why there is no spark?

Thanks.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 18, 2012, 12:56 PM

Post #9 of 11 (1203 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

Spark before and none now? Back. Check all electrical connections you removed to do this and fuses everywhere that should have power. If oil pressure switch* was disturbed or any wires pinched.

*Note sure on that but some can shut spark down.

?? Does distributor rotor turn? Shouldn't have been involved. Not much help but something in the process caused no spark if there before,

T
_________________________________________
Long retired now


bigelow
Novice

Jul 18, 2012, 5:55 PM

Post #10 of 11 (1181 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

All wiring appears to be connected properly. All ground wires are connected. Checked fuses. All seem fine.

I pulled the ignition coil off and used my Actron Autoanalyzer to test it per instructions out of a Chilton manual. I did not get any readings. So, I decided to go and get a new one. Prior to putting it on, I did the same test on the new one. No readings on it, either. I'm guessing I'm not doing the test properly. Does the coil have to be on the engine to test it? Since it's up underneath the intake manifold I took it off to test so that I could get to the connectors. If it has to be on the engine to test it, I'll reinstall it and try to test it that way.


bigelow
Novice

Jul 19, 2012, 12:35 PM

Post #11 of 11 (1133 views)
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Re: 88 GMC S15 2.5L TBI won't start after replacing head gasket [In reply to] Sign In

Update

  • Tested the pick up coil in the distributor. It tested good.
  • Ignition coil tested good.
  • Getting approx. 11.9 volts to the ignition coil from the ignition switch.

Still no spark.




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