Diesel swaps

[JeepSJ]

People have asked about swapping gas to diesel and they keep getting referred to the reference section. Well, that article really doesn't tell you much. Information that we need to compile are things like the components of the glow plug circuit (sensors, timers, etc...) changes to the fuel system (filters, heaters, return lines, lift pumps, etc...), and wiring the pump (fuel shut off and cold advance).

I'll be documenting all of this as I go through my swap, along with posting part numbers and such. If anyone has any information that they would like to contribute, I would certainly appreciate it. As soon as the swap is done and I have the information compiled, I'll be posting it here for future reference.

Please start posting your favorite part numbers now. Since this is a swap, aftermarket parts are totally acceptable. For example, aftermarket fuel filters seem to preferred over the stock ones, so how about listing what filter you are using. Same goes for lift pumps, and anything else you can think of.

Thanks in advance.

[NH2112]

Wiring the pump: I think the best way to do this is to use the gasser's + coil wire to energize the fuel shutoff solenoid. You could also tap into this wire for power to the HPCA/fast idle temp switch. I'm not sure if it's fused or not, though.

As far as the glow system goes, I'm just running a manual switch on my C1500, but if I was doing a swap I'd run the stock controller/relay.

The plumbing for the gasser fuel pump may work for the diesel lift pump since it seems to be in the same location relative to the crossmembers, etc. I don't know if the fittings are the same size, though. My fuel filter is a Racor 445 with 2 micron element and no heater or WIF sensor. If I was doing a swap now I'd use 2 of these filters, most likely mounted on a bracket on the right-side fender. One would have a 30-micron element and be on the suction side of the lift pump, the other would be on the pressure side and have a 2 micron element. Both would be heated. I still may do something like this, using the Model 80 filter from my K10 as the primary filter on the suction side and powering the sensors and heater with the coil wire, again. I'd use an inline fuse on the heater. I'm not sure of its wattage but 200W sounds right to me - that's 17A in a 12V system and definitely needs to be fused.

I don't have much of a preferred parts list, but here goes. Racor 45S fuel filter element (2 micron), Baldwin B7/Wix 51794/Napa Gold 1794 (2-quart oil filter.) Wix also makes an equivalent to the 45S filter, but I haven't used one. Next time I buy a filter I'll see which is less expensive.

[Blaine Hufnagle]

I'm also looking for a few more specifics for a gas-to-diesel swap, specifically in an '89 Sierra-Body, 5.7-TBI.

What parts can be re-used from the gas setup? I've already got a 700R4 tranny; I've been told that I may have to do some driveshaft work because the tranny will be relocated (backward, I'm guessing). True or no? I'm also thinking that the torque convertor from the gas motor will work, at least to get the truck running again. Truth to tell, about the only reaction from blowing up the tranny would be "Gee, darn." :D

I'm thinking that I'll have to dis-assemble the gas-engine wiring harness before ripping most of it out, in order to keep track of the wiring for the temp sender(s) and such. It seems logical to use the coil + wire to power the fuel cutoff solenoid; what else need I look for/at?

The one thing I'm concerned about with the wiring is how much of it goes through the gas ECM to drive the speedometer and other gauges. I don't know how integrated into the ECM the DRAC box is (that's what sends the speed signal). The gauge cluster takes me all of five minutes to remove and disassemble, so a new fuel gauge is easy (the hard part will be remembering to pull up to the diesel pump instead of the gas pumps!).

I'm not much worried about the glow-plug system. It rarely gets cold enough in Texas to need them, and I plan on having enough battery behind the starter to start my Detroit S60.

I've been told that we'll have to replace the gas tank; besides gasoline contamination, what's the issue here? This one's got a send and return line. Is there something else we're not seeing? Would the in-tank pump work for getting fuel to the injector pump, assuming the pressure was sufficiently regulated? A firewall or fender-mount fuel filter setup is a given. No part numbers yet, but that's easily fixed.

Will we need engine-specific throttle and TV (tranny) cables, or is there enough slack in the gas ones to reach the diesel bracketry?

A diesel-specific radiator is also pretty much a given, but since the truck needs a new radiator anyway, that's not much of an issue. Will we need to do any fabrication on the radiator mounts? Would a "heat-buster" gas-specific radiator work as well? There'd be no fabrication involved, but would it's capacity be sufficient? Note that I do practically no towing with this truck.

Since all the ductwork and valves for the A/C system are electronically driven, do I even need the vacuum pump, assuming we're also going to install a hydroboost brake booster? No vacuum lines from the gas motor cross the firewall, so I don't see the need....

Lastly, can all this be done in a weekend, assuming all the parts are on-hand?

Are there any bases I've not covered?

(The answers to all this will be directed towards my partner, who is most reluctant to do the swap.)

-blaine

[mirage]

Your transmission won't move, so you shouldn't need to change out your drive lines at all. The torque convertor in there may get you by, though I wouldn't recommend it. I'm sure someone else knows more about the consequences of using the gas TC.

Sounds like you're pretty set with the wiring set up. Just one wire to open the fuel up :).

I didn't think that they started the electronic speedos until after 89? Maybe it's different in a GMC...?

You'll still want the glow plug system. It's real easy to hook up a manual system, just a few wires. I can't remember the temp at which the glows don't automagically fire, but it's above any temperatures we've gotten here in phoenix.

I wouldn't think you would need to replace the gas tank, as people who accidentally fill their diesel tanks with gas don't need to replace their tank. Just give it a good flush and maybe add some two stoke oil to make the gas remains more diesel-like :). I would think the in-tank pump would be fine, but I'm not sure how it will hold up to the diesel fuel. I've got the pump outlined in one of the articles under my hood and don't have any problems with its given 6psi IIRC. I've got my stock filter setup, but I'm sure someone has info on better ones since you'll be starting from scratch in that area.

I'd try to get the 4 core radiator for the diesels, which will require hacking together some mounts for it if you don't want to replace what you've got. Too much heat kills.

Even with the ductwork electronically controlled, I'm pretty sure that all of the servos are vacuum operated, just take the electronic signal to open or close them. If you don't want the stock distributor type vacuum pump you can find electric ones in older ford cars and some european imports have them too.

As far as being done it a weekend, I couldn't do it, but if you've done a few engine swaps before I don't see why not. Plan on putting in some long days though. Fuel lines and little things always take a long time.

I'm likely to be wrong on some of this info, so hopefully someone that has done the swap can give better info. Good luck, and this info has my no liability because I don't know what I'm talking about attached :0D

[garysleeman]

I'm in the middle of doing the same swap as you except I have a donor vehicle which was a C motor and I am converting it to a J motor (no EMC). I've got the GM wiring diagram book out of the library and I can tell you don't need a computer to run the speedo. The TV cable and bracket are diesel specific and available through GM. I was lucky enough to purchase the last cruise control cable bracket available through GM. Plug the vapor canister line from the fuel tank and use the fuel supply and return lines cut off at the back of the block and run flex lines from there. The stock electric fuel pump can be used in place of the gasser fuel filter.
You are lucky if you never need to run a glow plug system. I wired one through a temperature switch and then eliminated it. I found in the summer even with the motor warm it started better with glow plugs. The only question I have is running the 700r4 with the J motor. There were 40 different ways that GM wired this transmission and the electric manual I have doesn