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Fueling: Aeromotive FRS fitted to an Aermotive 340 fuel pump (new), ID 725cc injectors. OEM carrier and fuel lines. Base fuel pressure is 40psi+
Problem: The cars fuel pressure is inconsistent at higher RPMs. Sometimes the car won't rev above 5krpms and then other times it is absolutely fine. We know it is fuel pressure related because the AFR gauge in the car leans out and goes null when we have this issue.
The tuner checked it on the dyno and said that there is an inconsistent fuel pressure issue and said it could potentially be the damper. The problem is that the fault is intermittent and the ECU is not throwing any related codes.
Before I start swapping out parts, are you guys able to help diagnose this fault. I recently changed out a walbro 255 to an Aermotive 340 fuel pump and the issue started occurring (but we are running more boost now). It has been triple checked that the fault is not with the installation of the fuel pump and the filter has even been removed temporarily to test.
Things we have tested so far:
- Possible fuel pressure issue. New pump, Aeromotive 340 was installed a few weeks ago. The fault did develop after then but i've had it removed and rechecked and it doesn't appear to be related to the install.
- Venturi swirl jet has been drilled out to 2.5mm - fault has not happened since then.
- There are no codes on the ECM/BCM which are showing which could rule out a sensor issue.
The car most of the time seems to run perfectly normally. It was checked on the dyno yesterday and ran fine there too. The tuner said it did have an irregular fuel pressure on idle and thinks it could potentially be the fuel damper. any thoughts?
The trouble is it's intermittent. The fault has not occurred all week. I have an uprev licence, I've been data logging and trying to find where the fault could be to no avail. Anyone have any thoughts on how to pin point issue.
I had a similar issue back in December/January. My car would start to lose fuel pressure in higher rpms then my ECU, ProEFI, would cut the car to base boost since the car was going lean. But the issue was inconsistent. Some pulls it would drop fuel pressure and on others it wouldn't. Turns out my fuel pump was going out, it was a single Walbro 485 at the time. I know you said the pump is new, but maybe you got a pump that is going bad already.
Also, what does your fuel system consist of? Are you using stock rails? What return fuel setup do you have?
I had a similar issue back in December/January. My car would start to lose fuel pressure in higher rpms then my ECU, ProEFI, would cut the car to base boost since the car was going lean. But the issue was inconsistent. Some pulls it would drop fuel pressure and on others it wouldn't. Turns out my fuel pump was going out, it was a single Walbro 485 at the time. I know you said the pump is new, but maybe you got a pump that is going bad already.
Also, what does your fuel system consist of? Are you using stock rails? What return fuel setup do you have?
Thanks for this
It's a Aeromotive 340 in stock carrier, CJM stg 0 FRS, stock fuel lines, Injector Dynamics 725cc. I think all else in fuel system is stock.
It did cross my mind that it could be the pump but the tuners are not convinced. It's still under warranty, not sure... hmm...
One noteworthy point is the original issue was thought to be the fuel filter being squashed at the bottom of the tank and then subsequently removed. We ran the car on the dyno and it ran 'fine' albeit a little lean (which was thought to be a mapping issue). Fast forward a few days later and the issue occurred again after a 3 hour drive. The next morning the car was absolutely fine! Argh..
Took the car back to the people who mapped it and they said the fuel pressure is inconsistent on idle as well as the top end and there is nothing wrong with the map (which the other garage thought it could be as did I). Put it down to potentially the fuel dampers, but i'm not sure which one of the two in the car. Thoughts?
Check you fuel injectors and see if they need cleaning with a flow match test. When I had a lean, misfiring fueling issue a few weeks back, it was just that.
I seem to recall people that had a damper issue had their cars hesitating at 2200 rpms. I don't run any dampers at all. I'm using stock rails with the ends cut off and -6 AN fittings welded on. As bluestream mentioned look into having your injectors cleaned. I still think it's likely a pump issue. But that's just my $0.02.
I think WTFMike is on to something with the pump being faulty.
Yesterday I went to start the car after a few days of not driving it. The fuel pump made a horrid noise on priming and i knew the car wouldn't start and as expected it didn't! Tried ignition off and re-priming an the pump wouldn't come on so I left it after a few attempts.
This morning I've tried it again and after a few attempts the car did start but it's clear there's something not right with the pump. Now i'm starting to think that this was the issue all along with the intermittent fuel pressure.
The pump is only a few weeks old and i'm looking to return it under warranty. There seems to be a mounting issue as the 340 pump is too big for the carrier and we're having to run without the strainer sock because it was being squashed and causing problems with fuel pickup and we suspected was the cause of the fuel starvation.
The question now in terms of next steps:
1. Do I swap it out for another Aeromotive 340 under warranty and run without a fuel stainer sock?
2. Do I go for the CJM Twin pump which I have been offered used?
The car is around 510bhp - 530bhp. IDC (725s) reaches 80% on high IATs. I may upgrade the SI to a TI due course but I've read on Aeromotive website that the 340's rating considering many different factors is around 700bhp which is plenty of headroom so is the CJM twin justified for this application?
What are your thoughts? Fingers crossed this was the issue all along. I did suspect this for a while as it only started happening since replacing the pump.
Personally, I'd buy the twin pump setup. It will give you room to grow. Because eventually we all want more power. I run the CJM twin setup with the 255/450 pumps. I've never had a aeromotive pump in my hand, but I assume it's the same length as the Walbro pumps. I know in the OEM carrier it's a tight fit with the Walbro pumps but I've always been able to run the strainer socks on them.
Personally, I'd buy the twin pump setup. It will give you room to grow. Because eventually we all want more power. I run the CJM twin setup with the 255/450 pumps. I've never had a aeromotive pump in my hand, but I assume it's the same length as the Walbro pumps. I know in the OEM carrier it's a tight fit with the Walbro pumps but I've always been able to run the strainer socks on them.
Thanks
With the CJM, were you able to plumb in without adding any spacers or anything? Will I need to replace the fuel lines and other bits to make it work?
Personally, I'd buy the twin pump setup. It will give you room to grow. Because eventually we all want more power. I run the CJM twin setup with the 255/450 pumps. I've never had a aeromotive pump in my hand, but I assume it's the same length as the Walbro pumps. I know in the OEM carrier it's a tight fit with the Walbro pumps but I've always been able to run the strainer socks on them.
They still aren't out for sale yet (Even though they said July they projected it to be out) for their revised version. I'm mad...
CJM has a newer revised version of their twin pump setup? What’s the improvements/changes on it?
Yup. They said this on the CJM website on the Twin pump.
"This product is undergoing design updates to support even more power. The outgoing model is out of stock. We apologize for any inconveniences. Please keep an eye out for the upcoming model. Expected release is July."
Still waiting because their previous version is unavailable for purchase.
Personally, I'd buy the twin pump setup. It will give you room to grow. Because eventually we all want more power. I run the CJM twin setup with the 255/450 pumps. I've never had a aeromotive pump in my hand, but I assume it's the same length as the Walbro pumps. I know in the OEM carrier it's a tight fit with the Walbro pumps but I've always been able to run the strainer socks on them.
A couple of weeks ago I replaced my Walbro 255 with a new Aeromotive 340 lph. and it fits the stock assembly no problem. Good luck getting this lean issue worked out.
A couple of weeks ago I replaced my Walbro 255 with a new Aeromotive 340 lph. and it fits the stock assembly no problem. Good luck getting this lean issue worked out.
do you have a pic of how you did it? I’m quite surprised- do you have a fuel return system?
i compared this to the Walbro 255 I have on my desk and it looks slightly smaller?
wonder how it compares to oem pump dimensions, anyone have these to hand?
08-02-2018, 02:44 AM
Vortech: Intermittent lean fuel pressure problem!
