Chevy and GMC Duramax Diesel Forum banner

Wehrli LML CP4 conversion

9K views 28 replies 21 participants last post by  denarli6.6 
#1 ·
I bought the Wehrli CP4 to CP3 conversion for a great price from Jason Wehrli and now I have some questions. Has anyone does this conversion on an LML that can lend some insight on the installation? I have a pump and a kit, a little lost on the hook up. I saw the CP3 installation on a sticky here but that is for Fleece, the kits are not alike. Thanks in advance. :help
 
#2 ·
The two kits are are very similar. Email Jason at Wehrli for instructions he will send them to you. Take your time and read and reread, this forum has lots of good information about the conversion. The sticky labeled CP3 conversations has good pictures and explanations.
 
#3 ·


That picture there is the most important. I just made it for you and the wehrli kit. The only real difference is the high pressure line enters the rear of the passenger side fuel rail.

With the cp3 conversion people have to realize the routing of the fuel lines.

1. you have fuel going into the cp3 (feeding it) and that comes from the fuel filter.

That goes into the 1/2 barb directly in the middle of the injection pump on the back of it.

2. You have a high pressure fuel line that the pump uses to feed the fuel rail. This comes out and goes into the back of the passenger rail. (youll need a m10 triple square tool to remove the existing plug)

3. The return. Whatever the cp3 doesnt use just goes back into the fuel tank.
 
#5 ·
Subd. Plan on doing this soon as well!
 
#6 ·
I have done this kit any questions pm me or text me your phone number I'll gladly help
 
#7 ·
Ive done it, got confused at one point and called up the shop, ended up talking to Jason and emailing him some pics. He got me squared away even though I am sure he thought I was an idiot lol. I had some silly questions. m10 triple square bits are key, found a set at NAPA in podunk nowhere Missouri at the last min but I suggest finding those before anything else as it is essential to the install. Anyone with issues just pm me as well and I will shoot you my number, if you have face time I can show you mine and give advice on what you got goin on if pics cant cut it.
 
  • Like
Reactions: mcullins91101
#8 ·
I'm getting ready to install mine soon. Any other special tools that will be handy other than the m10 triple square tool?
 
#11 ·
We used wobble extensions, 1/4" and flex end ratchet wrenches on the removal of the CP4 that made getting into the tight spaces so much easier, these were purchased at Harbor Freight and were really inexpensive. Also installed the billet filter blank by Fass, really easy task. If you need a picture of the tools we used, I can get a picture to you. Hardest part was taking all the lines out of the way and going back with the the feed line connections in the valley.
 
#10 ·
I was also considering doing the factory fuel filter delete at the same time. Is it worth it? I heard you hold better rail pressure if it's deleted.
 
#12 ·
I used crows feet as that was what I had access to at the time that worked for me. The worst part was the bolts holding the cp4/cp3 in place and the fuel feed line connection in the valley to reconnect.
 
#18 ·
I have my egr blocked with plates rather than fully deleted, can this kit be used if it is not fully deleted. Thank you
Mine is not fully deleted either I left the EGR in place and without a blocker plate I just have it turned off in the tuning. Will this kit or another work with my situation and a sportsman CP3 pump?
My shop told me today that the EGR has to come all the way out. They've done several of these CP3 conversions.
 
#16 ·
Mine is not fully deleted either I left the EGR in place and without a blocker plate I just have it turned off in the tuning. Will this kit or another work with my situation and a sportsman CP3 pump?
 
#17 ·
Good looking truck right there. Looks like mine without the lift. How does it ride.
 
#20 ·
If you cut the end of the hose at a 30 to 40 degree angle you won't get a condensation build up to freeze a 3/4 inch hole shut.
I don't live in Alaska or Canada where temps get in the sub zeros but here in the mountains we do get below freezing d have not plugged mine in 6 years


Sent from my iPhone using Tapatalk Pro
 
#22 ·
Guys I am stuck here. I got the Wehrli kit and cannot figure out how the fuel feed line hooks up if you are bypassing the factory filter. I have read the directions several times and just can't picture what it is saying. I have also dug around here and google to no avail. Can anyone help me out? trying to get this thing finished up today please help!
 
#23 ·
if the only issue is bypassing the filter, the best solution would be to not bypass the factory filter, the added water separation, filtration and ability to prime the fuel system is handy and theres really no benefit in removing it.

I do not know the answer to your question as asked though, so all i can do is give you the above advise and a bump.
 
#28 ·
You guys should check out the low pressure line I made / sell for bypassing the fuel filter on CP3 converted LML trucks. Look up John C Garage if you're on instagram for pictures and examples.

Also it can be purchased here.

https://underdog-diesel.com/collect...sion-low-pressure-fuel-line-kit-2011-2016-lml

It eliminates that two piece metal line under the y bridge. It will bypass the fuel filter, or can be used with the fuel filter with enough fuel line, but it definitely cleans thing up a lot!

Also, I'm the creator the CP3 conversion sticky thread here.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top