Lean only in boost

So I replaced the old stock fuel pump with a DeatchWerks DW200 pump. Had some issue with the fuel line leaking in the tank which is now resolved. Now my problem is when in boost the A/F gauge goes dead lean and car sputters. Car runs fine and A/f gauge is bouncing like normal as long as no boost is present. I pinched the return line and the fuel pressure shot up past 100 psi. The only change was installing the new pump. Only code is 15 speed distance sensor circuit but I wouldn't think it would cause this issue.

I have vacuum at the Accufab AFPR, so I assume it is seeing boost pressure too. New fuel filter - car ran fine before pump change. Any ideas on what to check next?

Thanks, Ralph

Background info: +20s injectors. StageII 86 GLHS LM, Accufab AFPR set to 28 PSI vacuum line on / 35 psi vacuum line off

First thing I notice is, you should be getting less pressure at idle with the vacuum line on, not more. But 28 psi at idle is really low IMHO. Shoot, with +40's in my 2.5, I'm still running 45 psi at idle.

If it's going dead lean in boost, somehow, the AFPR isn't adding pressure as your boost goes up. Or, at least that should be the most likely culprit. Can you extend the line on your fuel pressure tester, and tape it to the windshield where you can see it? That's the first thing I would do. Go out and step on it, and see if you fuel pressure is keeping up. My guess is, it's not. I believe from your other thread you said you replaced the fuel filter. I guess there could be a restriction someplace. Just because it can build pressure, doesn't mean it can flow the volume.

Is your LM a stock MP piece? The only other thing I could see happening is if your LM is actually a turbonator based cal, and somebody left the staging limiter on. But your simptoms would be a little different, it should fall flat on it's face at 4000 rpm with a bad speed sensor. I had this happen to me, so that's how I know. The staging limiter default is it turns on with 0 speed reference, and off once the car starts moving. If it never sees the speed change, it doesn't turn off the limiter, and you are limited to 4000 rpm. But that's not boost related, so I doubt that's your issue.

Anyways, it's a place to start. I'm sure other will chime in with their thoughts.

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Originally Posted by 83scamp

Just because it can build pressure, doesn't mean it can flow the volume.

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this is what i was going to suggest.. pressure isnt volume.

Quote:

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Originally Posted by 83scamp

First thing I notice is, you should be getting less pressure at idle with the vacuum line on, not more. But 28 psi at idle is really low IMHO. Shoot, with +40's in my 2.5, I'm still running 45 psi at idle.

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Whoops fixed. Got it backwards.

Yeah its a stock cal.

Check all your fuel lines front to back. Make sure that one hasn't gotten pinched at some point causing a restriction. The return is as important as the feed. Although a return issue will usually cause high pressure.

Either your regulator isn't keeping up, or the fuel volume isn't there. Pretty much your only choices...

Test the fuel pump volume.

http://www.turbo-mopar.com/forums/sh...liter-per-hour

Also

http://www.turbo-mopar.com/forums/sh...-fuel-pressure