# 1993 Chevy Problem!



## rtraider_88 (Jan 21, 2009)

*I have a 1993 Chevy C1500 TBI 4.3L V6 VIN Z pickup truck. The truck never starts in the morning hours after sitting all night however once the truck is cranked it will start up fine once it has been warmed up after first start of the morning. On first crank of the morning the truck cranks only if I press down on the gas pedal all the way! Then it follows with a nasty idle once started! The truck has no power what so ever going down the road and a very poor fuel economy along with a bad hesitation in throttle response. The truck also smells like straight gasoline! I have changed the fuel pump filter inside the tank and under the driver side door. I have also changed the MAP sensor, IAC, PCV valve, Spark plugs, Wires, Cap, Rotor, Spark control module, Coil, Coolant sensor, TPS, EGR, Fuel Pressure regulator, Injectors, and have replaced all gaskets on the throttle body. The timing chain has also been replaced. Timing is good it was checked with a timing light.. And no vacuum leaks were found! I looked as the distributer and the magnets looked O.K. nothing looked out of place. No check engine (MLP) Light..
Any suggestions would be helpful thank you for your time in advance*


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## mack1 (Nov 27, 2007)

Hi rtraider_88 and welcome to TSF,

Sorry for not posting earlier, was waiting for someone with experience on TBI systems to jump in. 

Here are my thoughts on your problem. 
You have covered almost all the bases, surprised you haven't found the problem yet. I think you are getting too much fuel into the intake. I suspect that either the PCM is holding the injector open too long or the regulator is leaking. Pull your dipstick and smell the oil. If the regulator is leaking, you can get gas in the oil pan. I had this happen on a 96 blazer. You could smell gas under the hood but no leaks were seen. Per my book (which starts at 1994) the regulator is mounted inside the fuel meter to it's cover. Book says it has a *strong* spring and uses a gasket. That gasket might be leaking. 

You can use a noid light to see the pulses from the PCM to the injector by probing at the injector wires. Use a straight pin or small bare wire to probe the wires at the connector while connected. Push the pin down beside the wire into the connector. You should get the light flashes during start and while running. If you have a friend with a TBI system, compare the flash length with theirs. 

Hope this helps,
Mack1


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## rtraider_88 (Jan 21, 2009)

Hello Mack1 yesterday i changed out the ECM and ran it for a test drive .. However it didnt fix the problem the truck was still very sluggish {poor preformance} i just changed the oil a few days ago.. The oil was black that i changed and i always keep the oil changed ive never seen it that dirty... I dont know why it was so bad its never looked that bad, but im with you i think a little gas drained down in there and cleaned out my block thats why it was so dirty... thats the only think i can think of...


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## mack1 (Nov 27, 2007)

Hi rtraider_88,



> The oil was black that i changed and i always keep the oil changed ive never seen it that dirty... I dont know why it was so bad its never looked that bad, but im with you i think a little gas drained down in there and cleaned out my block thats why it was so dirty... thats the only think i can think of...


Did you do the "smell of the dip stick" test? That would be a dead giveaway. 

Also, did you move the Eprom over to the new ECM/PCM? It has the right settings for your fuel mixture and other data. If it was used and from the same year, model, eng, etc. it will probably work with out switching the Eprom. 

Have you done a compression test yet? Low compression will make an engine sluggish.

Best regards,
Mack1


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## rtraider_88 (Jan 21, 2009)

yes i done a compression test... they all ranged from 150 to 180. As for the ECM i used my old eprom .. I did smell of the dip stick ..to me it had a hit of gas.. but to me oil has a hit of gas so im not real sure..lol


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## rtraider_88 (Jan 21, 2009)

:sigh:


rtraider_88 said:


> yes i done a compression test... they all ranged from 150 to 180. As for the ECM i used my old eprom .. I did smell of the dip stick ..to me it had a hit of gas.. but to me oil has a hit of gas so im not real sure..lol


Also i ment to add i checked the oil about a hour ago and it was about 2 inches above the dip stick full line... i dont know if they added to much oil when it was in the shop or if gas has drained down in the oil :sigh:


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## mack1 (Nov 27, 2007)

They probably just overfilled it with oil. 2 inches over full is a lot. Unlikely you have that much gas in oil without being able to smell it very well. In any event, get someone else to smell the oil. A second openion always helps. One thing is for sure, you can't drive much with gas in oil without doing damage to the rings and bearings. 

Best of luck,
Mack1


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## markster57 (Jan 25, 2009)

have you checked the fuel pressure , i have been working on my 95 1500 4.3 and it had the same problem , i found that the fuel pressure was at 4psi , to low need 9 to 14 psi


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## rtraider_88 (Jan 21, 2009)

Hello markster57 I have been wanting to check the fuel pressure however i dont have have a fuel pressure gauge but im looking for one.. I just replaced the fuel pump pressure regulator and the injectors. However one of the parts that i put on could have been defective.. Did yours just not want to crank in the mornings? Did it smell like straight gasoline when at idle? Thanks


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## markster57 (Jan 25, 2009)

i did not have any fuel smell , but i had my wife turn the key on as i was holding the fuel pressure gauge on the fuel line at the filter , i have replaced my pump and it is the best it has ever ran


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## markster57 (Jan 25, 2009)

i pulled the bed bolts out but one of them , i backed it off then used a jack to lift the bed , it made it easy to get the pump out , better then dropping the tank, it about 1hr to do the job


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## markster57 (Jan 25, 2009)

markster57 said:


> i pulled the bed bolts out but one of them , i backed it off then used a jack to lift the bed , it made it easy to get the pump out , better then dropping the tank, it about 1hr to do the job


hey have to check to see if the fuel pump relay is working , you can bypass the relay by using a jumper wire from 78 to pin 30 , look on the bottom of the relay for pin #


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## rtraider_88 (Jan 21, 2009)

Hello markster the fuel pump relay is working i can hear the relay cut on when i turn the key... I am going to do a fuel pressure test today to see what the pump is doing. I done a vacuum test yesterday and it gave me a steady reading of 20... I also done another compression test the results were as following
CLY 1	180 PSI
CLY2	160 PSI
CLY3	170PSI
CLY4	180PSI
CLY5	165PSI
CLY6	160PSI
I will let you know how the fuel pressure test turns out... Thanks for your time


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## markster57 (Jan 25, 2009)

your compression looks real good ,good lluck


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## rtraider_88 (Jan 21, 2009)

yea but there is a 20 psi drop from cly 2 to 4 and from 4 to 6.. fuel pressure test showed 15


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## markster57 (Jan 25, 2009)

that 20 psi is ok , if it was at 110 or 100 that could be a problem , it still sound like you have a problem in the tbi , i would check it again , it must be leaking into the intake manifold ,flooding the engine in the morning


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## markster57 (Jan 25, 2009)

have you pull the tbi off and check the bottom of it to make sure there not cracks or a area were it might leak, i have found problems like that on carb's ,where i had mix up some eproxy and repair it , they did the same thing , over night the fuel would drip into the manifold


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