Mechanics

CHEVROLET S-10 SENSOR PROBLEM

1994 Chevrolet S-10 • 210,000 miles

Truck turns over fine (strong battery) does not start. Fuel pump replaced 2 weeks ago (ran for 2 weeks, no problem). Checked fuel pump by connecting jumper from battery to plug terminal provided by GM on drivers side of engine compartment, fuel pump runs ok. Still thinking mabe a fuel problem, opened throttle plates & sprayed starter fluid into intake knowing it should run for a second or two, nothing, did not try to run. Checked for spark going to plugs, have fire. Pulled plugs, checking for fouled plugs. Plugs in great shape. Ok mabe firing while starting engine but not in run position. Turned switch to on position, checked for power to coil, 12.2 volts.I am baffled, with fire & gas it should run, if only for a few seconds. Please help, I need my job, I need this truck. Thanks
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Wayne1994
December 21, 2012.



Scan for codes and check fuel pressure first 9-11psi. Check dist cap for being cracked or pull coil wire to see if spark going to cap if it is replace cap and rotor in dist. Check undtbi unit for blown gasket by spraying choke cleaner there once it runs it cold be a bad module in ignition it can be tested at auto parts stores.

Hmac300
Dec 21, 2012.
If there was no spark from coil to cap I would have no fire at the plugs correct? I DO have fire at the plugs. Module mabe, but again from past experience, when module goes thats it! No more fire to plugs until its replaced. As far as spraying cleaner around base of TBI I got your reasoning. That won't work until its running and I think I mentioned that I opened the throttle plates and sprayed into the intake, attempting to start it. I'm not an expert but I do have a little experience from the past, mostly "old school hotrods".
Thanks for your input.
Thinking that the "spark" at the plugs may be weak, I have a new coil, wires, cap and rotor and plugs on the way (time for tune up anyways). Another point I need to check may be the crank sensor? Mabe check the timing chain, pull up #1 (compression stroke) on TDC and see if both valves are closed. Again I'm old school all this onboard computer/sensors kind'a intimidates me, so I'm most likely taking the simple and making it harder that it is. Need to get back to basics I guess. Hey thanks again for your suggestions.

Tiny
Wayne1994
Dec 21, 2012.
What engine is in this so I can help you a little more I fyou can spray choke cleaner in the tbi then it's not a fuel problem becaue it would start. Disconnect themap sensor and see if it will start. You dont'have a crank sensor on that engien ifit's a v6 if you go to the site here and look under tune up it willcover how to diagnose your system as it has several systems there.

Hmac300
Dec 23, 2012.
Sorry forgot. Its a 1994 S10 with a 4.3L engine V6. Again whats really throwing me off is the fact that I have fire at plugs and cannot start it for a few seconds by opening the throttle plates, spraying directly into intake. The parts arrived, AC Delco CR43TS plugs, MSD cap and rotor, MSD coil and new wires. I know I didn't need them but it was time for tune up anyway so why not. Trying to cover what I can, I found the fuel pump relay (under the dash on a 94) and have 11.6volts to the relay. The horn relay is right beside it, same type, swaped them and both relays work. And I agree with you, does not seem like a fuel problem, but then again the pump went out 2 weeks ago, changed it and everything was dandy for two weeks. And by checking voltage to the pump relay with switch on (voltage present) that eliminated the switch as well. The pump I bought was from Advance Auto, hey I had no choice, had to bum a ride to get there, but I have one on hand now, a Delpa that I got from NAPA. Should be OEM.
Now you suggested disconnecting the MAP sensor, ok, not sure exactly where it is but it should be on top of the intake somewhere. I was able to borrow a vehicle so at least I got wheels for now. Thanks for taking the time to respond.

Tiny
Wayne1994
Dec 24, 2012.
The map sensor is on the firewall with a vacuum hose going to it. Ifyou disconnect it and the truck starts then scan for codes or you should hve already to see where your prolbem are a is. If you don't know how to do it take apaper clip an dcross a& B at the aldl turn key on and count flashes. It will be like 1 flash 3 times then 2 flashes 3 times that wold be code 12 then go to site here and look under obd1 tourble codes. Also as you have an msd system recheck your installlation.

Hmac300
Dec 24, 2012.
Already attempted to get code using the paper clip method, have done this in the past. It is a 12 pin plug under the dash that only utilizes 3 of the slots (A and B plus one more) I could not get the flashes. Should have, as you said done the code 12 three times(code 12 meaning the diagnostic is working). The ECM is under the hood on top of coolant reservoir. I read somewhere if thats the case, I would have OBD 1.5 and not OBD 1. Wherever I read that article stated that OBD 1.5 cannot be tested in this manner. Going to unhook the MAP and also check out another theory of mine today. But hey, its Christmas, and like I said, I was able to borrow a vehicle. So please enjoy and have a MERRY CHRISTMAS
I'm not giving up, I'll figure this out sooner or later, reminds me of marriage vows."For better or worse". Thanks

Tiny
Wayne1994
Dec 24, 2012.
You don't have obd1.5 it has a 14 pin connector. Check your fuses underhood.

Hmac300
Dec 24, 2012.
Went ahead and installed the fuel pump from NAPA along with a new inline filter. The map sensor is located on the intake, passenger side near the TBI. Roughly 1 1/2" wide, mabe 3 1/2" long, one vacuum line and a 3 pin plug. Unhooked it tried to start engine, no change at all, never started. I do not have an MSD system, just a stock replacement coil from MSD and cap and rotor. Ever known an ignition module (HEI) to mabe be weak but not completly gone? All the ones I've ran across when they go they go out completly.
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Tiny
Wayne1994
Dec 24, 2012.
Yes that can as well as pickup col in dist, check resistance of pickup coil if I remember correctly it shold bein 600-900 ohm range. I think those module in dist can be checked at an auto parts store but they wen tbad as well. Also dist cap would go at coil mount an dprevent from running. Have you gone to the site here an dgone through the step by step on how to diagnose your system? I'd bet not as I said to do that at the very first post

Hmac300
Dec 24, 2012.

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