1994 GMC Sierra 4.3 v6 TBI no start

Asked by Mar 26, 2017 at 03:33 PM about the 1994 GMC Sierra 1500 K1500 SL 4WD Standard Cab LB

Question type: Maintenance & Repair

I have good, blue spark - it is getting fuel, timing is set, compression has been tested and is good.  Have replaced M.A.P. sensor, engine coolant sensor, new distributor / cap / rotor and new coil + new spark plugs and plug wires.  Checked to see if valves were opening, etc, with valve cover off.  All seems to be set perfectly.  Fuel delivery is also good.  The only code I am getting is for low voltage to the knock sensor.  This should not prevent the engine from starting.  Please help.

12 Answers

87,035

How do you know it is getting fuel? You would need someone turning the key to start, turning the engine over to see if fuel is getting threw the fuel injectors. Try spraying some starting fluid down the TBI or just a very little gas and see it it starts.

I have some help - we can watch the TBI sending fuel while cranking engine. Have also tried starting fluid while cranking.

87,035

Did you check for spark at the spark plugs?

Yes. It is baffling me. We used spark tester along with pulling a plug and watching spark while cranking.

87,035

This should be starting. Do you have a timing light?

Wasn't sure if timing light would help when it is only cranking. Will try this later tonight. We have watched valve actuation and checked timing mark along with setting distributor to line up with firing order. Have checked and rechecked firing order.

87,035

Ok, the timing light will work while turning it over. Remember to disconnect that brown wire for the timing advance. Make some marks on the timing marks so you can see. If you have the proper fuel pressure, and the compression is around 150 lbs. this should start.

Compression is 150 on all but #4. It is around 125. Will try the timing light to confirm timing with brown wire unplugged. (took a while to find that thing, it was under the dash / glove box area taped to wire loom)

87,035

Good. Just so you know the fuel pressure should be 9 to 13 lbs. I mention this because without the proper fuel pressure, it will not start also. If you get to the point of checking it let me know so you can test the fuel regulator.

Found a vacuum leak by chance - internal. Pulled manifold, replaced gaskets, put all back together and set timing w/ light while cranking. Still not starting. Will have to borrow a tool to check fuel pressure. Will see if I can get that done tomorrow... Appreciate the help so far.

87,035

Thanks, here to help.

It's running! Finally! On a hunch, we began testing each individual plug and plug wire. We found we weren't getting consistent spark and some were not sparking at all. We tested the wires and they were good. Changed out the brand new plugs for more new copper core plugs and it sprang to life. Either we somehow fouled a full set of new plugs, or, they were bad out of the box. We were only testing #1 to get timing, etc. Thank you for your assistance and your time.

Your Answer:

Sierra 1500

Looking for a Used Sierra 1500 in your area?

CarGurus has 10,273 nationwide Sierra 1500 listings starting at $5,795.

Postal Code:

GMC Sierra 1500 Experts

  • #1
    dragonflyoffshore
    Reputation
    5,640
  • #2
    John Saffrahn
    Reputation
    4,010
  • #3
    Glenn Clingenpeel
    Reputation
    3,780
View All

Related Models For Sale

Used Ford F-150
132 Great Deals out of 11,559 listings starting at $3,900
Used Dodge Ram 1500
35 Great Deals out of 521 listings starting at $2,500
Used Chevrolet Tahoe
11 Great Deals out of 793 listings starting at $5,900
Used Toyota Tacoma
22 Great Deals out of 1,728 listings starting at $6,413
Used GMC Yukon
18 Great Deals out of 1,035 listings starting at $5,500
Used Jeep Grand Cherokee
59 Great Deals out of 5,326 listings starting at $2,994
Used Chevrolet Camaro
11 Great Deals out of 922 listings starting at $11,500

Used Cars For Sale

2019 GMC Sierra 1500 For Sale
91 listings starting at $42,835
2018 GMC Sierra 1500 For Sale
12 Great Deals out of 8,051 listings starting at $26,275
2017 GMC Sierra 1500 For Sale
8 Great Deals out of 346 listings starting at $25,708
2016 GMC Sierra 1500 For Sale
14 Great Deals out of 358 listings starting at $21,750
2015 GMC Sierra 1500 For Sale
5 Great Deals out of 435 listings starting at $19,990

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.