20 Most Recent 1991 GMC C2500 Questions & Answers

Here is the firing order diagram for the 5.0 liter (305), 5.7 liter (350) and the 7.4 liter (454) V-8 engines (note position of locking latches/screws between the 3 and 6 and the 1 and 2 terminals on the distributor cap). Let me know if you need the 4.3 liter V-6 engine diagram (hopefully not in a 2500 series truck) or if you require any further assistance.

Hi, differential fluid lubricates and cools the differential, some have friction modifiers to prevent clutch chatter in limited slip differentials. As for U joints. Improper installation could result in a vibration or drive line shudder, usually during acceleration but would not likely cause poor performance/acceleration or engine "chugging" and for the fuel smell you have you should return to the shop that installed your new fuel tanks and ask them to have a look at it.

sounds like a bad u joint,they will have a vibration frequency that makes them vibrate at different road speeds

Try changing the map sensor. I had a Buick do the same it a map sensor took care of it.

For the 1991 GMC C2500 5.7L V8:

Firing Order:
1-8-4-3-6-5-7-2

Cylinders:
.......(back)........
|...8............7...|
|...6............5...|
|...4............3...|
|...2............1...|
.......(front)

Distributor:
(+)..6....5
3................7
4................2
......8....1..(+)

Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!

sounds like you have plug wires off by one cylinder, rotate the wires 1 position each way on the dist. cap until you have it right,...

Under the hood in a black box. You sure it's fuel problem? Will it start if you spray carb. cleaner in the throtle body?? If it is a fuel problem, It's probly the pump.(in the tank.)

Could be a bad coil - check that?

still you can fix the problem but for this you need the help of repair manual with its help you can easily solve the problem because it will guide each and every thing how to do the work http://toolsnyou.com/

START CAR, WAIT 3 MINUTES, DRIVE CAR 4 15 MIN 3 TIMES