Tuner can't tune my cai and has given up on me.

[markmurfie]

Did a quick search and couldn't find anything on replacing the mustang gt fuel filter. Is it a hard job? And is there any way to test the fuel pump?

https://www.mustang6g.com/forums/threads/fuel-filter-replacement-diy.105071/
I've never done one personally. This might just be GT350 only.

The pump and regulator are accessible under the rear seat.
Bad regulator, or a burst fuel line in the hat assembly are other things.
I would look into getting a hat ring tool. hammer and chisel work but mess it up pretty good.
https://www.freedomracing.com/310-123-fuel-tank-sender-unit-wrench-j-45722-9340.html
bit pricey for most people probably, but thats the one I got. It works great.

The only real test would be to put a pressure gauge on it, and theres no shrader valves to do so. It would have to be added inline.
The next test I can think of is to flow test it. Which would be a crude timer and bucket to see. you would need a way to command 100% tho. Some tuners can send tank drain tunes.

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[K4fxd]

Here is a screen shot of my bad LU47's

I feel stupid not recognizing this pattern, won't happen again.
This is after MANY attempts to get the trims correct.

 

[markmurfie]

Here is a screen shot of my bad LU47's

I feel stupid not recognizing this pattern, won't happen again.

This is after MANY attempts to get the trims correct.

Yup, thats the "slope" of the injector being off. Which changes with fuel pressure... which shouldnt change much.

The other side of that is manifold pressure, which does change alot, but is inffered from MAF on our cars. Which is done through a quadratic curve, so be carful with that as well. Its hard to tell what is truly causing it in a single datalog or no tune change, just that there is a mismatch some where. The original JLT file and +30% MAF revision here was telling, its on the fuel side.

 

[K4fxd]

I sent my injectors to the local automotive tech school, they tested them and said they were junk.

 

[markmurfie]

Usually bad injectors, will misfire causing a miss that can be constant or intermittent. They could also stick open causing a bank to bank fuel imbalance. With a quickly fouling plug in a cylinder.

If they just flow less than expected, they could be dirt/ clogged, but it would be rare to have that on all of them at the same time. If they were badly flow matched you would get the same fuel imbalance bank to bank.

Im not really that good of a diagnostic tech .

 

[K4fxd]

Im not really that good of a diagnostic tech .

I used to be a pretty good one. Back before electronic carbs....

The problem I had is the fueling was never consistent. I would do a log and things would look good. Take another and it would be way out of whack. I ended up chasing my tail for several weeks. The up side is I now have a mechanical fuel pressure gauge. GT350 fuel rail and an auto meter gauge.

Anyway I hope the OP gets things figured out.

 

[markmurfie]

For all I know, OP could still have left over E85 in his tank, tring to run a 91 tune.

 

[tdstuart]

For all I know, OP could still have left over E85 in his tank, tring to run a 91 tune.

I’ve done a good amount of back and forth and refills on 91. Just ran a full tank of 91 and refilled. I’m sure if I put the JLT on it will still show the same

 

[Red65]

Just a spitball here but if OP possibly has some junked-up injectors, wouldn't the fuel pump's duty cycle be higher under WOT than normal?

 

[markmurfie]

Just a spitball here but if OP possibly has some junked-up injectors, wouldn't the fuel pump's duty cycle be higher under WOT than normal?

I think it's very granuler, like 60%dc at low demand and 100%dc at high demand.

In the picture I posted you see as air mass goes up it gets leaner, then goes back to 10-15%.

 

[Zrussian13]

Did a quick search and couldn't find anything on replacing the mustang gt fuel filter. Is it a hard job? And is there any way to test the fuel pump?

K4 is right. There isn't a serviceable fuel filler on the GTs. Just the sock on the pump.

 

[tdstuart]

I think it's very granuler, like 60%dc at low demand and 100%dc at high demand.

In the picture I posted you see as air mass goes up it gets leaner, then goes back to 10-15%.

Here are data logs on stock injectors, didn't solve the issue.
https://www.dropbox.com/s/ebafdybfe34gadi/stock inj JLT 91.hpl?dl=0
https://www.dropbox.com/s/5pj6as143gcc1sc/stock inj, stock intake 91.hpl?dl=0

 

[K4fxd]

I think Mark is thinking it is a fuel pump issue. Log fuel pump commanded DC

I think there is a problem with your JLT.

 

[markmurfie]

Here are data logs on stock injectors, didn't solve the issue.
https://www.dropbox.com/s/ebafdybfe34gadi/stock inj JLT 91.hpl?dl=0
https://www.dropbox.com/s/5pj6as143gcc1sc/stock inj, stock intake 91.hpl?dl=0

So you got a tune for stock injectors and JLT? Are you going to get a revision? We assume the MAF values should show 95% higher at the same periods if its 120. I don't see that, only about 50% added over the stock intake tune values

The stock intake stock injectors log, I was assuming it was the stock tune until I saw 7800+rpm. Fuel for that log looks good.
30 minutes later, the JLT log was created, but Im not confident the tune you had in it was correct.

 

[tdstuart]

So you got a tune for stock injectors and JLT? Are you going to get a revision? We assume the MAF values should show 95% higher at the same periods if its 120. I don't see that, only about 50% added over the stock intake tune values

The stock intake stock injectors log, I was assuming it was the stock tune until I saw 7800+rpm. Fuel for that log looks good.
30 minutes later, the JLT log was created, but Im not confident the tune you had in it was correct.

That is the exact log for the tune my tuner sent me for the JLT 120mm. If you look at the first tune they sent me for JLT a while back ago you can see that the maf also showed low to mid 30s. Then in revisions they changed the maf curve to boost it to high 40s, but the fueling didn't change much.

I sent them the logs and they responded with:
"Unmetered air is getting into the engine.

I would ditch your new intake or have someone diagnose it as something is off somewhere on the car allowing unmetered air to enter the engine."

I'm pretty sure I have patched the leak well enough it should not cause 30% fuel adjustment. The only other thing I can think off is the sound tube not being blocked but to my knowledge that doesn't have any impact at all. I think on Tuesday I will be able to get a smoke machine to check if it's leaking from anywhere else, or if my patch really isn't sufficient enough.

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