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Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 7792
Experience:  Have owned a repair shop for 25 yrs.
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Chevrolet C3500 HD 1991 chevy 3500 with 454 fuel injected.

Customer Question

1991 chevy 3500 with 454 fuel injected. seems to be overfueling at lower R.P.M.s. I have already replaced the E.G.R. valve. I recently had a short in the wiring but this problem happened about 5 hours after the short in the wiring
Submitted: 3 years ago.
Category: Chevy
Expert:  JHoop replied 3 years ago.
Hello , my name is JHoop and thank you for choosing justanswer.com. Please tell me all the problem as my answers are based on the information you provide.

What tooling do you have to diagnose this and what is your level of expertise?
Customer: replied 3 years ago.
I've got a pretty good back ground in mechanics on big stuff and some older model cars and trucks I don't have any diagnostic equip. only a multi tester . My 1991 chevy 3500 with fuel injected 454 began to start over fueling just like a manual choke was applied the E.G.R.is clean the air filter is clean I checked the fuses
Expert:  JHoop replied 3 years ago.
Is the truck near you?
Customer: replied 3 years ago.
no my truck is not here
Expert:  JHoop replied 3 years ago.
Can you have the truck and the computer near at the same time soon?

There are several things that can cause your problem
Customer: replied 3 years ago.
yes what do you need me to do
Expert:  JHoop replied 3 years ago.
Get back to me when you have the truck and computer there. I can walk you thru diagnosing this.
Customer: replied 3 years ago.
ok, The distance between my laptop and truck is about 300 ft. and thats as close as I can get this may be a slow process with me walking back and forth .
Expert:  JHoop replied 3 years ago.
Let's do this first. I am here most of the day. I need you to do a code check for the engines computer. Do you know where the data link connector is? Under the dash on the drivers side.

Then grab a paper clip and pull the codes. CLICK HERE for that test.
Customer: replied 3 years ago.
I'm not able to locate the 12 pin terminal on pass. side ,I located 16 pin terminal on drivers side , do I have to remove any of the dash to get to the 12 pin terminal I understand the procedure when I find the terminal
Expert:  JHoop replied 3 years ago.
It is screwed to the back side of the dash. near the steering wheel.
Customer: replied 3 years ago.
I have located the computer , But I still can't find a 12 pin data link the plug going into the computer is a12 pin , There is only a 16 pin data link for a code reader any other suggestions other than getting a code reader.
Expert:  JHoop replied 3 years ago.
You sure it's a 1991?
Customer: replied 3 years ago.
Yes I just looked at the title to confirm
Expert:  JHoop replied 3 years ago.
It can't have a 16 pin in that year. 16 pin data link started in 1995 as OBD2

Does that connector look like this?
graphic
View Full Image
Customer: replied 3 years ago.
Yes
Expert:  JHoop replied 3 years ago.
WOW...... That is a first for me OBD 2 on a 1991. Is the computer a small steel colored box behind the glovebox and has only TWO connectors?
Customer: replied 3 years ago.
No, It's on the right side of the steering column with one 12 pin connector,I don't know the exact dimensions but it's around 2" thick 6" wide and maybe 8" long
Expert:  JHoop replied 3 years ago.
Look behind the glove box above the blower motor. Is there a computer 2 connectors only?
Customer: replied 3 years ago.
This will have to wait until tomorrow as it is dark and starting to rain,any words of wisdom and will I be able to contact you tomorrow without any additional charges
Expert:  JHoop replied 3 years ago.
I will keep your question open. You can get back to me anytime answering any e-mail sent to you related to this question or by logging into your JA account. Thanks again, JHoop
Customer: replied 3 years ago.
O.K. I found the computer with 2 plugs it was behind the glove box, Now what?
Customer: replied 3 years ago.
O.K. I found the computer with 2 plugs it was behind the glove box, Now what?

Expert:  JHoop replied 3 years ago.
You need to tell me what color the wires are to the data link connector.
Customer: replied 3 years ago.
Are you refering to the plug with 16 pins on the drivers side
Expert:  JHoop replied 3 years ago.
Yes
Customer: replied 3 years ago.
O.K. I've got 7 wires and the colors are RED,WHITE,TAN with black stripe,BROWN with white stripe,WHITE with black stripe,BLACK with white stripe,and ORANGE with black stripe
Expert:  JHoop replied 3 years ago.
OK. With the key in run jumper the white/black wire to the black/white wire and perform the code retrieval test I sent you. Let me know the results.
Customer: replied 3 years ago.
O.K. The light flashes once then 2 times fast I let it cycle 9 times it didn't change
Expert:  JHoop replied 3 years ago.
OK. There are no codes stored. Code 12 is a system check code.

Can you tell me more about the short in the wiring?
Customer: replied 3 years ago.
The power lead from the battery to the junction box on right side firewall shorted out by the right exhaust manifold,The wire has been repaired. I have some other points of interest , after repairing the wire and getting back on the road my trucks exhaust got alot quieter it was leaking between the crossover and manifolds, Could the convertor of been plugging up to create excessive heat which maybe melted the casing on the wire and maybe damaged the O2 sensor but that should show up as a code?

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Tim's Auto Repair
Tim's Auto Repair
Mechanic
7872 Satisfied Customers
Have owned a repair shop for 25 yrs.