Fuel Pressure issue related to stalling? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

xtahoex · 09-18-2018, 11:00 AM

Hi everyone... Did some searching and could find anything definitive, so here it goes.

I have a Datsun with S15 SR20DET swapped. The ECU was tuned by Enthalpy and I have been working with them to solve this issue. But, I might be at a stalemate right now.

The issue I am having is the car is stalling on deceleration. Enthalpy has told me that my fuel pressure should never dip below 45 psi, under deceleration I am at 40 psi.

I am using a stock FPR. With vacuum disconnected it jumps to 51 psi, with vacuum connect it sit at 45 psi at idle. At 9lbs of boost I show 60 psi of fuel.

Bottom line Enthalpy tells me that fuel pressure should be set at 45 psi with the vacuum disconnected.

Could any of this be related to my stalling issues?

Thanks

5280VertDET · 09-18-2018, 01:19 PM

There's a vac leak somewhere, built a vac leak tester. It's PITA to track down, but that what it sound like to me.

also,

See if you can test with known good FPR.

xtahoex · 09-18-2018, 09:12 PM

I guess I should have added that I have done the following trying to chase down the problem...

New coolant temperature sensor
Verified that the Z32 MAF and TPS were within spec and that TPS was adjusted
Cleaned and adjusted IACV
Lengthened intake tube in between MAF and Turbo
New fuel pump and added Prosport electronic fuel pressure gauge
Completed boost and vacuum leak tests and repaired several leaks

Thats why I am down to either an issue with the FPR or a tuning issue? Can anyone think of anything else?

The car starts and idles like a champ, it accelerates good, it's only on deceleration with the clutch in is when fuel pressure drops to 40 PSI and the car stalls out.

Can anyone verify what their fuel pressure is in a similar situation under deceleration with clutch in?

Ryan

Datsun freak · 09-19-2018, 08:27 AM

Bad blow off Valve unless you’re not running one now

xtahoex · 09-19-2018, 08:54 AM

I removed the too. Running no BOV right now.

Datsun freak · 09-19-2018, 09:01 AM

Now that I remember I had similar issue with my Jim wolf ecu , I was able to get rid of the stall at decel by changing settings in my safc , cant recall what settings I had to play with I just went off What I got from searching safc tuning , safc has air deceleration setting you can adjust to compensate enough to keep her in under decel

http://forums.nicoclub.com/afc-air-d...p-t312068.html

Datsun freak · 09-19-2018, 09:06 AM

http://forums.nicoclub.com/afc-air-d...p-t312068.html

5280VertDET · 09-19-2018, 09:30 AM

Which ECU do you have?

xtahoex · 09-19-2018, 11:15 AM

Stock S15 ECU tuned by Enthalpy.

Datsun freak · 09-19-2018, 11:30 AM

Get an afc and adjust air decrease settings

Search safc air deceleration settings on google

5280VertDET · 09-19-2018, 11:48 AM

Quote:

Originally Posted by xtahoex

Stock S15 ECU tuned by Enthalpy.

Yea, thanks, I mean what is the code of the ECU?

If it's an auto ECU deceleration is different.

xtahoex · 09-19-2018, 11:54 AM

It's a 6 speed ECU... I don't have the code for it right now.

Enthalpy is going to send me a new ROM. Hopefully they can make the adjustments to the tables because I don't want to run piggyback.

Datsun freak · 09-19-2018, 12:37 PM

Quote:

Originally Posted by xtahoex

It's a 6 speed ECU... I don't have the code for it right now.

Enthalpy is going to send me a new ROM. Hopefully they can make the adjustments to the tables because I don't want to run piggyback.

How long has the tune turn around been from enthalpy? I might have to get one sounds like you get pretty fast turn around

xtahoex · 09-19-2018, 01:19 PM

Quote:

Originally Posted by Datsun freak

How long has the tune turn around been from enthalpy? I might have to get one sounds like you get pretty fast turn around

The turn around was good. About a week and I live in California and they are in Florida. I decided on enthalpy vs a piggyback and although there have been a few issues (most of them are on my end) Martin has been very helpful and is reachable by phone or email.

Are you currently driving in a Datsun? If so, what type?

Datsun freak · 09-19-2018, 01:28 PM

Quote:

Originally Posted by xtahoex

The turn around was good. About a week and I live in California and they are in Florida. I decided on enthalpy vs a piggyback and although there have been a few issues (most of them are on my end) Martin has been very helpful and is reachable by phone or email.

Are you currently driving in a Datsun? If so, what type?

I’m running a 67 1600 with a KAT setup , I’m on a Jim wolf ecu now but have been waiting about 3 weeks for them to send me back my distributor for a reclock .

I’m looking for other ways to get it done now I have a feeling something is wrong . I went on the enthalpy site I’ll give him a call and get a tune from him.

I bet if I order a tune today it’ll get here before Jim wolfs reclocked distributor does .

xtahoex · 09-20-2018, 12:54 PM

Quote:

Originally Posted by Datsun freak

I’m running a 67 1600 with a KAT setup , I’m on a Jim wolf ecu now but have been waiting about 3 weeks for them to send me back my distributor for a reclock .

I’m looking for other ways to get it done now I have a feeling something is wrong . I went on the enthalpy site I’ll give him a call and get a tune from him.

I bet if I order a tune today it’ll get here before Jim wolfs reclocked distributor does .

Very cool. I'm running a 71 Datsun 1200 Sedan with a 510 independent rear swap.

Kingtal0n · 09-20-2018, 04:28 PM

1. pressure test
2. Run a Recirculated Bypass

fixed

gota watch the wideband to see where it goes when you lift for diagnosis. Chances are that air is moving backwards through the compressor and interfering with the maf signal.
It isn't common on sr20 because the manual trans ecu have a fuel cut when TPS goes to 0%. So maybe your tps is not adjusted correctly for this.

Like someone said, SAFC has a minimum decel air function that people can use on MAF cars to limit max airflow during low throttle percentage%.

The question is, is this the cause of your symptom, and why. It could be plumbing related, turbo related, (maf tube) etc... Or it could be something else of course we can't see from here.That is why wideband diag is necessary.

09-18-2018, 11:00 AM	#1
xtahoex Join Date: Nov 2017 Location: CA Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	Fuel Pressure issue related to stalling? Hi everyone... Did some searching and could find anything definitive, so here it goes. I have a Datsun with S15 SR20DET swapped. The ECU was tuned by Enthalpy and I have been working with them to solve this issue. But, I might be at a stalemate right now. The issue I am having is the car is stalling on deceleration. Enthalpy has told me that my fuel pressure should never dip below 45 psi, under deceleration I am at 40 psi. I am using a stock FPR. With vacuum disconnected it jumps to 51 psi, with vacuum connect it sit at 45 psi at idle. At 9lbs of boost I show 60 psi of fuel. Bottom line Enthalpy tells me that fuel pressure should be set at 45 psi with the vacuum disconnected. Could any of this be related to my stalling issues? Thanks

09-18-2018, 01:19 PM	#2
5280VertDET Nissanaholic! Join Date: Aug 2013 Location: Denver Age: 37 Posts: 2,052 Trader Rating: (14) Feedback Score: 14 reviews	There's a vac leak somewhere, built a vac leak tester. It's PITA to track down, but that what it sound like to me. also, See if you can test with known good FPR. __________________ S13 Vert \| SR \| PE1420 \| 5-Speed \| 15x9.5 - 0 \|

09-19-2018, 09:30 AM	#8
5280VertDET Nissanaholic! Join Date: Aug 2013 Location: Denver Age: 37 Posts: 2,052 Trader Rating: (14) Feedback Score: 14 reviews	Which ECU do you have? __________________ S13 Vert \| SR \| PE1420 \| 5-Speed \| 15x9.5 - 0 \|

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09-18-2018, 09:12 PM	#3
xtahoex Join Date: Nov 2017 Location: CA Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	I guess I should have added that I have done the following trying to chase down the problem... New coolant temperature sensor Verified that the Z32 MAF and TPS were within spec and that TPS was adjusted Cleaned and adjusted IACV Lengthened intake tube in between MAF and Turbo New fuel pump and added Prosport electronic fuel pressure gauge Completed boost and vacuum leak tests and repaired several leaks Thats why I am down to either an issue with the FPR or a tuning issue? Can anyone think of anything else? The car starts and idles like a champ, it accelerates good, it's only on deceleration with the clutch in is when fuel pressure drops to 40 PSI and the car stalls out. Can anyone verify what their fuel pressure is in a similar situation under deceleration with clutch in? Ryan

09-19-2018, 08:27 AM	#4
Datsun freak Join Date: Sep 2018 Location: Socal Age: 34 Posts: 21 Trader Rating: (0) Feedback Score: 0 reviews	Bad blow off Valve unless you’re not running one now

09-19-2018, 08:54 AM	#5
xtahoex Join Date: Nov 2017 Location: CA Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	I removed the too. Running no BOV right now.

09-19-2018, 09:01 AM	#6
Datsun freak Join Date: Sep 2018 Location: Socal Age: 34 Posts: 21 Trader Rating: (0) Feedback Score: 0 reviews	Now that I remember I had similar issue with my Jim wolf ecu , I was able to get rid of the stall at decel by changing settings in my safc , cant recall what settings I had to play with I just went off What I got from searching safc tuning , safc has air deceleration setting you can adjust to compensate enough to keep her in under decel http://forums.nicoclub.com/afc-air-d...p-t312068.html

09-19-2018, 09:06 AM	#7
Datsun freak Join Date: Sep 2018 Location: Socal Age: 34 Posts: 21 Trader Rating: (0) Feedback Score: 0 reviews	http://forums.nicoclub.com/afc-air-d...p-t312068.html

09-19-2018, 11:15 AM	#9
xtahoex Join Date: Nov 2017 Location: CA Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	Stock S15 ECU tuned by Enthalpy.

09-19-2018, 11:30 AM	#10
Datsun freak Join Date: Sep 2018 Location: Socal Age: 34 Posts: 21 Trader Rating: (0) Feedback Score: 0 reviews	Get an afc and adjust air decrease settings Search safc air deceleration settings on google

09-19-2018, 11:54 AM	#12
xtahoex Join Date: Nov 2017 Location: CA Posts: 13 Trader Rating: (0) Feedback Score: 0 reviews	It's a 6 speed ECU... I don't have the code for it right now. Enthalpy is going to send me a new ROM. Hopefully they can make the adjustments to the tables because I don't want to run piggyback.

09-20-2018, 04:28 PM	#17
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	1. pressure test 2. Run a Recirculated Bypass fixed gota watch the wideband to see where it goes when you lift for diagnosis. Chances are that air is moving backwards through the compressor and interfering with the maf signal. It isn't common on sr20 because the manual trans ecu have a fuel cut when TPS goes to 0%. So maybe your tps is not adjusted correctly for this. Like someone said, SAFC has a minimum decel air function that people can use on MAF cars to limit max airflow during low throttle percentage%. The question is, is this the cause of your symptom, and why. It could be plumbing related, turbo related, (maf tube) etc... Or it could be something else of course we can't see from here.That is why wideband diag is necessary.