LT4 HPFP quality issues?

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Oct 5, 2020 | 11:27 AM

Pekka_Perkeles

Thread Starter

Burning Brakes

Joined: Oct 2005

Posts: 1,089

Likes: 82

From: Kauhava, Finland

LT4 HPFP quality issues?

Got a really strange issue with a customer car (2014 LT1) with some upgraded components for LT4 supercharger, E85, LT4 injectors, Dsteck aux low pressure fuel pump and so on.

With supplier delivered LT4 hpfp fuel pump, a rail pressure was a problem from the beginning, until stock GM LT1 hpfp was put back on the car.

Details, logs, tune and screen shots are here:

https://forum.hptuners.com/showthrea...ne-not-running!

Anyone experienced anything similar?

Oct 5, 2020 | 11:30 AM

Pekka_Perkeles

Thread Starter

Burning Brakes

Joined: Oct 2005

Posts: 1,089

Likes: 82

From: Kauhava, Finland

Oct 6, 2020 | 09:49 AM

Jjagg0125

Pro

Joined: Jul 2016

Posts: 748

Likes: 40

I had a fuel rail pressure problem and I thought it was a failed check valve on the aux fuel system. Added a check valve, no help. Then diagnosed it was either the hpfp or a injector. Swapped the injectors and works perfect now. The car was hard to start due to the injector leaking by and emptying the fuel rail.

Oct 7, 2020 | 09:36 PM

C7&7

Le Mans Master

Joined: Mar 2010

Posts: 7,052

Likes: 945

From: DFW TX

Yea I had similar issues and it was the lt4 didn’t have the right lash cap and was bottoming out and eventually failed. Did you mean sure for the correct lash cap?

Oct 8, 2020 | 10:26 AM

TJay74

Safety Car

Joined: Nov 2011

Posts: 3,715

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From: Norman OK

Quote:

Originally Posted by C7&7

Yea I had similar issues and it was the lt4 didn’t have the right lash cap and was bottoming out and eventually failed. Did you mean sure for the correct lash cap?

If this is the stock LT1 cam you dont need a lash cap when using the stock LT4 HPFP on it. The lash cap is only needed when running an aftermarket cam with the +32 or +38 fuel lobe.

Oct 9, 2020 | 11:18 AM

Pekka_Perkeles

Thread Starter

Burning Brakes

Joined: Oct 2005

Posts: 1,089

Likes: 82

From: Kauhava, Finland

Quote:

Originally Posted by TJay74

If this is the stock LT1 cam you dont need a lash cap when using the stock LT4 HPFP on it. The lash cap is only needed when running an aftermarket cam with the +32 or +38 fuel lobe.

This car is with stock LT1 cam.

We'll try new LT4 HPFP pump in couple of days.

Jan 29, 2021 | 01:06 PM

Pekka_Perkeles

Thread Starter

Burning Brakes

Joined: Oct 2005

Posts: 1,089

Likes: 82

From: Kauhava, Finland

Well, this was a tuning issue. Considers only 2014 model year and do not copy all LT4 hpfp settings. Leave Pulse Params/Peak duration as stock.

Happy tuning!