My CUCV spin on fuel filter mod

Whitfield

Member
115
0
16
Location
Richmond Virginia
Duramax Fuel Filter installed and up running. Line size @ filter is closer to 1/2 inch but fresh 3/8" line will stretch into place over the Duramax inlet & outlet. I do have the fuel heater wired up using new DIY weather pack connectors. I have not wired up the water separator yet as I wish to modify the Duramax design to retain the CUCV 3rd wire / bulb check function.
 

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drewzee87t

Member
70
8
8
Location
MO ozarks
New filter set using technoweenie parts list

I went with the setup TechnoWeenie posted (THANK YOU!!)

The parts list is all correct except there is one part numbers that amazon mis-labeled, make sure you get the correct ones. I believe it was one of the 3/8" adapters. If you are paying attention when you order it won't make sense and you can switch it to proper size. I put it together exactly like TechnoWeenie did, I just spliced lines in to the existing fuel lines.

I did not need any kind of adaptor, fabbed up metal plate or anything, it just bolts right up using existing bolt as per my picture. I bleeded it and the bleeder valve works perfect, the ball valve works perfect. The total cost was around 117 USD. I would go with a shorter filter as it is almost impossible to screw on this really long filter when it is full. I primed that huge filter with the lift pump and it only took about 10-15 seconds cranking. The check valve worked perfect, one person operation.

Truck started up once the bit of air in the small fuel hose to the IP was filled.

Next day test, the truck started right up fine.

Will check when I am next home. No leaks, no problems, very easy. No fabricating or bs it just fits right there. Highly recommended.

I had the stock fuel filter and have been struggling for years now with losing prime when not starting truck in a while. At first it was like a month and it wouldn't start, or on a steep hill. Over the years :), it has gotten to the point where I can't even use it. It will lose prime in a couple days, and it requires so much cranking to bleed it and get it started that it was becoming like a two day job to get the **** thing going. Then it would be dead in 2-3 days and more charging, etc. I finally gave up and replaced it. I wish I had done this a long time ago. Pic of final install attached.

Thank you technoweenie :)
fuel_filter_cucv.jpg
 

drewzee87t

Member
70
8
8
Location
MO ozarks
There is no heater and no sensor. The electronics are disconnected. If that's important to you then the filter housing has an extra port that you could use for a heater. The water sensor, I don't think so.

I had a dead truck, so frustrated I was going to get rid of it. I change out the filter, now it works. **** the cartridge filter and all the junk. In ten years I didn't even know it had a heater in it and never got a indicator to drop water.

If that's important to you get a OEM one and like many others here, it will fail the same way. I had the typical water sensor rustout leak. I could have jb'd a penny into it, maybe I should have, but that seemed like the wrong way to go.

It do get cold here in missouri during winter, but it ain't alaska. Winter temps around 15F usually in the AM. If it's below zero I am probably screwed.

If I knew now what I didn't know then....I would not have bought this finnicky relic truck. It has been (less than) cheap and a pain in the ass to keep running. These things seem to always go together. If you want a new diesel truck with all the goodies, go buy one. If I had my way, I would have been better of with a gasser, with a regular 12v system and etc. I got this for 2800 or so in 2009 with 65000 on the clock and maint. records from fort leonard wood. Over the past ten years I have put new GP's, new GP solenoid, one battery (the army issue one is at least 12 years old and still going), a manual GP switch when the GP controller card went, new inner fenders, the headlight mod, a Tacho, heater core, radiator, and now a fuel filter system. That's pretty much it. It has been pretty cheap to keep around, but it's unreliable as ****, primarily due to this issue. I figure I have less than 5k in this POS and around here, somebody savvy looking around could probably find a beater truck that can do highway speeds with an interior and radio and stuff for about that. I am stupid. I am okay with that because my truck is pretty badass if you don't mind the noise and slow driving.

I will be keeping this truck forever, most likely. I have a kit to somewhat sound deaden the cab and put rubber floor mats in, and that's it until the next thing breaks. I use this truck mostly to mess around, short trips to town, wood cutting and fetching, and whatever on the farm it can do. I probably drive it less than 800 miles a year. The axles and diff's are what's worth anything on it. Plus it's fun.

Peace

If the SHTF, I am looking at some alternator rebuilds and I am good to go. Have parts.

I will post back over time.
 

dillehay

New member
1
0
1
Location
Springhill Tn
Duramax Fuel Filter installed and up running. Line size @ filter is closer to 1/2 inch but fresh 3/8" line will stretch into place over the Duramax inlet & outlet. I do have the fuel heater wired up using new DIY weather pack connectors. I have not wired up the water separator yet as I wish to modify the Duramax design to retain the CUCV 3rd wire / bulb check function.
Sorry to bring up an old thread.....I just did this modification to truck yesterday. Though I would start here with question......Can you help with detail on which electrical lines you hooked up for heater and water indicator? Thanks in advance.
 

CA_LEO

Member
58
1
8
Location
Grass Valley, CA
Duramax Fuel Filter installed and up running. Line size @ filter is closer to 1/2 inch but fresh 3/8" line will stretch into place over the Duramax inlet & outlet. I do have the fuel heater wired up using new DIY weather pack connectors. I have not wired up the water separator yet as I wish to modify the Duramax design to retain the CUCV 3rd wire / bulb check function.
How’s this setup holding up for you? I think I like this one best.
 

drewzee87t

Member
70
8
8
Location
MO ozarks
Hey fuel system peoples!

I have same problem even after replacing the fuel filter with a custom setup. I am still taking on air and after a day or two after running, it will start right up, for like 5 seconds and then dies. Will not start again unless charged and cranked enough to push the air through, then it starts and runs great, but loses prime again. Now loses prime just overnight.

So it's not leaking in filter housing anymore (old housing was leaking from water sensor).

How can I find out if my leak is on the supply line/lift pump side, or the post filter lines to the IP? I am ready to tear out the intake manifold on this and thinking it could also be the line between the lift pump and filter, or even the mech pump has a bad check valve, etc. There are a million ways to lose prime it would seem.

Can anyone get me a way to prove out which side of the system is leaking or bleeding back to the tank?

I also am aware of some scary GM tech bulletin saying you need to replace the fuel pump AND housing pressure cold advance assembly on the IP itself must be replaced due to check valve issues allowing fuel to bleed back to and de-prime. This seems extreme to me, as truck runs fine once primed to run.

Please let me know if you can think of anything? I will probably have to go through all of this and replace it, but how can I test, say, if my mechanical fuel pump is leaking back to the tank?

or if there is a return line problem? I have been suffering with this for years and thought I had it figured out. Please help.

Thanks

Drew
 

emeralcove

Member
Steel Soldiers Supporter
133
10
18
Location
Battle Ground/WA
drewzee87t, my set up is post #236 and nothing that many others have done before me. I had real headaches with losing prime and was determined to solve the problem because I didn't like running the starter so much and getting out over and over to bleed air out of the fuel line every morning. I ordered my filter with a hand primer which I think the Duramax filter has as well. The primer works extremely well and using the starter to bleed air out isn't needed. But after bleeding the air out the first time it never gets used, nice to have though if there ever is an issue and you aren't near civilization when you need to prime the fuel line. I am pretty certain the mechanical pump has a check valve and except for a total PITA to change they aren't expensive. If the diaphragm is leaking and causing the loss of prime you could be leaking diesel fuel into the crankcase which isn't good either. I even experimented to see if I could see if any thing helped and found if it was parked front down hill it didn't lose prime as easy as parked front up hill. Good luck, it is frustrating but once you find the problem, it is hard to remember what a pain it was.
 
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shotty

Active member
Steel Soldiers Supporter
201
49
28
Location
Northern VA :(
Replaced my box fuel filter the other night which must have angered the gremlins in the filter base. It started leaking terribly bad.. next day I did the spin on setup with the wix base and a napa filter.

I used the stock mounting bracket, cut off at the bend, then welded a few bolts on to it for spacers. Some nuts and washers and I have a nice solid 3 point mount. I could have gone shorter on the bolts but it matches the stock spacing from the firewall.

My truck wasn't hard to start but it starts noticeably quicker now with the new filter. I'd say that having an air leak even if it doesn't put a bunch of air in to the lines still causes issues with the injection pump when it doesn't have pressure before the engine is cranked. I had a small fuel leak and thought the truck started fine but now I know what it should be like.

IMG_20201119_141149.jpgIMG_20201119_141215.jpg
 
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