6.2 diesel to gas engine.

custodian · Jun 15, 2019

I bought an 85 SWB with an AT and 6.2 diesel and will be switching to a 350 gas. I'll be replacing the gas tanks. Will the wiring harness have to be replaced? Anything else that will need replacing? ETC?

1987 GMC Jimmy · Jun 15, 2019

I’m assuming this is going to a run of the mill carb, HEI setup? No fancy EFI, TBI, etc.?

custodian · Jun 15, 2019

Yes, Carb and HEI. Nothing fancy. Giving this truck to my youngest granddaughter.

Rickf · Jun 15, 2019

Should be able to adapt the 6.2 harness to gas. Injector pump wire will power the HEI, water temp sender may need extending, if the carb has an electric choke you'll need to supply a switched & fused 12 volts. Won't need glow plug wires.

bucket · Jun 15, 2019

Rickf said:
Should be able to adapt the 6.2 harness to gas. Injector pump wire will power the HEI, water temp sender may need extending, if the carb has an electric choke you'll need to supply a switched & fused 12 volts. Won't need glow plug wires.

This sounds right. I've been told a few times that the harness is roughly the same, just different lengths on some connections.

Dmack · Jun 15, 2019

Mine has the conversion before my son bought it. Hope you do a cleaner job. They had pulled the ignition switch off the column, then drilled two toggle switches in the dash for ignition on and starter engage. The harness was butchered. I swapped in a factory harness.

custodian · Jun 17, 2019

Thanks. Sounds very straight forward. Will not cut any wires.

K5ride · Jun 17, 2019

I deleted my post due to misinformation.

Blue Ox · Jun 17, 2019

The 6.2L is not the Olds diesel. I has Chevy bolt patterns.

Hondo78 · Jun 17, 2019

bucket said:
This sounds right. I've been told a few times that the harness is roughly the same, just different lengths on some connections.

The 6.2 tanks should work fine with a carb I'm sure the diesels don't have a fuel -pump in them.

Blue Ox · Jun 17, 2019

You'd probably do well to change the pickups if you have evap. Also, the screens on diesel pickups are different. Don't know if that would cause a problem, but they have a relief valve that gassers don't.

K5ride · Jun 17, 2019

@ Blue Ox......... OOPS...... your right. After seeing your post, I looked it up and it was the 5.7 diesels that were made by Olds. I guess my memory isn't as good as it used to be....LOL.

Hondo78 · Jun 18, 2019

K5Ride

Easy mistake: The 5.7d and 6.2d Diesels were originally great engines for the time, however back then GM had a planned obsolescence plan that cheapened the original concept. A former neighbor now 90 years young, had both his original Oldsmobile 5.7 diesel wagon and a GMC 6.2 diesel step-side half ton, till he stopped driving last year. He was an Oldsmobile engineer on the diesel program.

custodian · Jun 29, 2019

Any tips on starting a diesel that has been sitting for along time? Going to see if it runs before I take it out.

Blue Ox · Jun 29, 2019

Is it in the truck?

6.2 diesel to gas engine.

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