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Discussion Starter · #1 ·
1994 GMC C1500 ext cab. 5.7L
I ran out of gas on the way to the station, I put in 1 gal of fresh gas and it started right away but on the way I had to rev it up a bit. 1 mile to the station then I put in 10 gal of gas and STP fuel inj. cleaner, still ran rough and not able to idle. No smoke or excessive fuel.
Next day, Heet water remover, changed fuel filter, and plugs, still runs rough.
I checked EGR last night and it works.
Please help.
Thanks
RG
[email protected]
 

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Are you getting a check engine light?

You should check it for codes. Sometimes it stores them even though the light may not have come on, or stayed on.
 

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Discussion Starter · #3 ·
94 GMC out of gas and running rough

I'll check it out. Do I need a special device to read it or is this a matter of shorting two pins together? If so, could someone explain where the pins go and which pins get shorted?
Thanks
Rick
 

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Discussion Starter · #4 ·
additional info

I didn't explain very well that when I put in the 1 gal. of gas it ran rough right away. I revved it up a bit to about 4k rpm intermittently to get momentum.
It ran rough the moment I put in the 1 gal. and restarted.
I also took off the air cleaner to observe the fuel being sprayed into the bowls and it was fine.
EGR- I pulled it off, put a vacuum on it and it held for two minutes just fine.
I'd be interested in understanding what happened when I find the bad part.
I'm wondering if I blew something when I revved it up?
Rick
 

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If the truck very quickly ran out of fuel and abruptly stopped, instead of petering out, the timing may have gotten thrown off my a tooth or two. On my uncle's Dadge Caravan, he ran over an 18-wheeler driveshaft and it tore the gas tank to shreds. Long story short, the sudden and abrupt stop of the engine caused the timing to get thrown of and he had to get a new belt installed and have it re-timed. Hope this isn't the case for you :|
 

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If the truck very quickly ran out of fuel and abruptly stopped, instead of petering out, the timing may have gotten thrown off my a tooth or two. On my uncle's Dadge Caravan, he ran over an 18-wheeler driveshaft and it tore the gas tank to shreds. Long story short, the sudden and abrupt stop of the engine caused the timing to get thrown of and he had to get a new belt installed and have it re-timed. Hope this isn't the case for you :|
It's a possibility, but the 5.7 engine doesn't use belts. The belts are much more pliable, they tend to flex and stretch, easier than a chain will.

As far as checking for the codes, you can stop by a local autozone (if you have one), and they can pull the codes for you for free. If there are no local autozones then you can do it yourself with this:
http://www.troublecodes.net/GM/
 

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Ran out of gas and now runs rough. Check the fuel filter theres a good chance you picked up trash from the tank and now its in the filter or possibly the pump.
 

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Discussion Starter · #8 ·
Thanks TrailLeadr. I'll try it tonight when I get home.
If I disconnected the battery for approx. 10 secs then reconnected it, would the codes still be stored? And if not, would the code reappear upon first attempt at a failed start or run?
Rick
 

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Could be a clogged injector. Take that air cleaner back off and find an old timing light and hook it up just like you would to check your timing.

Now point the light at the fuel spray coming out of the injectors. It should have a nice cone pattern to it. If it doesn’t you need to have the injectors cleaned professionally or send it out and have it cleaned.

When you disconnect the battery for more than a minute you loose all stored codes. If the problem is still there and the check engine light is still on or flashing then you still have a problem.

And yes you can use the old school paper clip trick on the 94’s. it’s the last year you can do that, now for the newer ones you need an ODII reader, most parts stores have them on loan.
 

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Discussion Starter · #10 ·
Okay, next idea please.
I checked with jumper and I got the "service engine" light when key turned to on did "flash" pause "on steady"
I checked the cononical form of the jets and they are cones that spray bursts timed exactly out of phase, or opposite timing, i.e. left right left right. The higher the RPM the faster they spray.
Sounds like timing is great! in Park (or Neutral) and when idle is coming down and gets to 900 rpm's it drops off abruptly.
No ability to idle.
The strong spray would sound to me like the fuel filter is fine (new) and the flow is fine.
 

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Discussion Starter · #11 ·
Map

Is it possible the MAP sensor went out and I didn't really run out of gas?
I just stalled while driving?
I'm looking at a "sensor" that comes off of the EGR valve and has three vacuum line type hose fittings and an electrical plug. One line comes from the EGR, it goes out to the body of the carb and a third has nothing on it. Is it possible that a hose fell off?
This unit is mount high on the engine (passenger side) just under the air cleaner but over the valve cover.
The MAP sensor's I"ve seen have only one line on them.
Is this third fitting for testing?
It looks like line in/ line out/ extra line.
Rick
 

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Discussion Starter · #12 ·
TrailLeadr,
Just curious, have you read my recent post? and, I'd be interested to see what you think.
Rick
 

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Discussion Starter · #14 ·
Yep!

Sounds like you're describing the EGR solenoid


Does it look like that?
Yes it does.
so what is the extra fitting for ? Testing?
And, where would my MAP sensor be?
And, (sorry for so many questions), could it be my MAP sensor went out and it only acted like it ran out of gas? or could my revving blown it some how?
Curious.
 

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Watch the fuel spray as the engine dies. If the fuel shuts off before the engine dies, you have an electronic problem. By the way, if the container you used to add the gallon of gas had water or old fuel, that will cause drivability problems until the crap is purged from the system. If you know anyone with an OBD-1 compatible scanner, check the data stream. It'll tell you a lot.
 

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Discussion Starter · #17 ·
I'll do it tonight. When you say electrical, could it be the MAP sensor?
As for crap in the sys I immediatly swapped out my fuel filter. Are you thinking may it still passed junk?
Rick
 

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And yes you can use the old school paper clip trick on the 94’s. it’s the last year you can do that, now for the newer ones you need an ODII reader, most parts stores have them on loan.
I have a 1995 Suburban with a 5.7L and I use a jumper wire to get the codes. Are you sure that 1994 was the last year for that?
 

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95 had what they called OBD1.5 It was still the same PCM essentially, but the plug in most models (not all) looked like the OBDII plug.

But you're right, you should be able to do the paper clip jumper on your year too.
 
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