Gas to Diesel swap, question on fueling

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

idrivea2002golf

Junior Member
Joined
Feb 19, 2025
Posts
20
Reaction score
29
Location
San Diego
First Name
Spencer
Truck Year
1981
Truck Model
C20
Engine Size
Not sure yet.
I'm reaching to the forum for recommendations/feedback/thoughts on fueling systems. I've been on the different square body forums looking up the function of the dual tank and the Pollack valve. Seems pretty straight forward. I don't like that it relies on the suction from the engine's mechanical pump for priming, I'd like to have a more proactive fuel supply. For reference truck is a 1981 so I have the 6 port with the motorized valve. I'm currently planning on swapping in a 7.3 idi out of a 90 F350.

Here's where I'm looking for feedback, as I see it I have two options:

Option 1: I keep the existing system as it is (obviously check for functionality and replace anything broken). Use the ON-OFF-ON momentary on the dash for the switching as it already does. In this case I would add an in-line fuel pump (diesel style) between the Pollack valve and the engine's mechanical pump. This would tie into the ignition system. Simplest option but I know these pumps make noise and I don't know if I'm going to want to hear it all the time. Chineseum pumps are 20-30$, Holley or AEM are 200ish.

Option 2: swap the fuel senders I currently have (1981 models) with senders/pumps from 1987+ and basically run two in tank pumps through the Pollack valve. This would require I swap the dash switch which isn't all that difficult. I like that this gives me pump redundancy as the in-line pumps can be fickle. Obviously more up front cost but really not terrible in the grand scope of this build. From my understanding the wiring is the same between the 1981-1986 and 1987+ at the valve, just need to tie in the sending pumps power lines. This also gives me the flow/pressure required for a diesel as I can get the 6.2 in tank pumps. Each pump is about 110$ on rockauto. So similar price to a quality (Holley) inline.

Option 3: something I'm not seeing?
 

ali_c20

Full Access Member
Joined
Sep 20, 2016
Posts
1,474
Reaction score
2,111
Location
Austria
First Name
Alexander
Truck Year
1974, 1979
Truck Model
C20, K5
Engine Size
350, 350

Frankenchevy

Proverbs 16:18
Joined
Jan 3, 2018
Posts
6,189
Reaction score
8,005
Location
USA
First Name
Jeremy
Truck Year
Square
Truck Model
CUCV
Engine Size
Small
Also, 87+ also have baffled tanks to go with the in tank pump. May not matter, but something to consider.
 

Broken85

Member
Joined
Jan 14, 2024
Posts
38
Reaction score
28
Location
Cumberland, NJ
First Name
A
Truck Year
1985
Truck Model
K10
Engine Size
350

righteous project I drive. Check out this thread I started. I recently switched over to in tank electric pumps. I think I solved a lot of the questions you have, but maybe not all of them. FYI, the inline pump after the pollak valve did not work. It was not able to pull enough fuel through the pollack with just a siphon because those inline pumps push fuel, and not really pull at all. I had to start all over with in tank electric pumps.

To your other point. Dual redundancy, can’t beat it. So my relay wiring that I also individualized power to each tank as well
 
Last edited:

idrivea2002golf

Junior Member
Joined
Feb 19, 2025
Posts
20
Reaction score
29
Location
San Diego
First Name
Spencer
Truck Year
1981
Truck Model
C20
Engine Size
Not sure yet.
Thou shalt not put them Ford parts into Chevies. ;D

The 1990 7.3 uses a mechanical fuel pump to feed the injector pump. Using the mechanical fuel pump that is on the engine would be the easiest way. No new sending units, no wiring work on the valve. Replacing a broken mechanical fuel pump is easy, can be done everywhere.
My 0.02$
https://www.rockauto.com/en/catalog/ford,1990,f-350,7.3l+445cid+v8+diesel,1126549,fuel+&+air,fuel+pump,6256
Not to split hairs... but TECHNICALLY it's an International Harvester part connected to a ZF part connected to a Borg Warner part. :D Although I'm going to replace the borq warner part with a New Process part.

Plus, no worse than people putting a Dodge part (6BT) in a square body. Actually, I would argue the 6BT is worse given it is an inline 6, both Chevy and Ford use V configurations.

Silliness aside, the mechanical pump works but it's suction is crap. I'd like to find a more proactive fueling supply especially since switching the pollack valve could possibly introduce air if the unused tank isn't primed.
 
Last edited:

idrivea2002golf

Junior Member
Joined
Feb 19, 2025
Posts
20
Reaction score
29
Location
San Diego
First Name
Spencer
Truck Year
1981
Truck Model
C20
Engine Size
Not sure yet.

righteous project I drive. Check out this thread I started. I recently switched over to in tank electric pumps. I think I solved a lot of the questions you have, but maybe not all of them. FYI, the inline pump after the pollak valve did not work. It was not able to pull enough fuel through the pollack with just a siphon because those inline pumps push fuel, and not really pull at all. I had to start all over with in tank electric pumps.

To your other point. Dual redundancy, can’t beat it. So my relay wiring that I also individualized power to each tank as well
Red3833's post with the diagrams and explanation of using the sniper output is kind of the swap I was thinking about doing.

I appreciate the feedback on the inline. My biggest concern, especially since I'm going to be dealing with a diesel, is having the inline pump not have enough suction.

I think I'm going to do the dual in tank setup.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,895
Reaction score
7,157
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Red3833's post with the diagrams and explanation of using the sniper output is kind of the swap I was thinking about doing.

I appreciate the feedback on the inline. My biggest concern, especially since I'm going to be dealing with a diesel, is having the inline pump not have enough suction.

I think I'm going to do the dual in tank setup.
if you use the original fuel pump on the engine, you should use the ford pollack valve, since it was designed to suck diesel through the valve when not running
vs the pollack on these trucks was intended to support fuel being pushed through it
 

Forum statistics

Threads
44,951
Posts
972,112
Members
37,834
Latest member
Seibelc1077
Top