Fuel Pressure Woes....

[Booztd 3]

Guys

I dont post my tech issues too often, but this ones got me scratchin my head....

Car ran mid 10's last year when I put it up in late october........changed nothing, sat over winter.

I went over everything and took it out the other day, first WOT pull it started to go lean so I got out of it. Luckily, had a fuel pressure gauge in the car, and noticed when it starts to go around/above 60psi the pressure falls rapidly (to below 40) base/idle pressure is set to 38...standard 1:1 rate FPR

Naturally I started thinking I've got something causing some blockage, so I pulled out both fuel pumps and checked the socks, also pulled apart the inline AN filter, as well as the FPR....found nothing

I was also curious if the FPR was acting funky, so when the car at idle, i disconnected the vacuum line and dialed my air compressor down to 25psi (verified with an aftermarket boost gauge) and gave the FPR 25psi of shop air, and it seems to hold the pressure just fine.

I'm starting to lean towards my fuel pumps potentially dying, or a blockage in one of the lines. The lines are all SS braided...

I also went back and checked the AEMlog.....looked at the battery voltage

I've got a lot of load on the battery/alt.....The battery is moved to the trunk, with 1 gauge wire going to the alt. I've got 2 electric fans, the relays for the fuel pumps, and all the other misc stuff, and I never seem to make more than around 12.5V, high boost I see it dip to around 11.9 or so, however I have tested the alt/bat and they come out "OK" on the testing equipment.

Also, I remember back when I trapped 136, the battery voltage was the same, so I dont believe its an actual power issue with the pumps not being able to keep up...

I was just curious if anyone had some recommendations on a decent method of troubleshooting fuel pressure issues....

Thanks

[Carl H]

leaky line in the tank perhaps...you are running ethanol fuel.

[Booztd 3]

leaky line in the tank perhaps...you are running ethanol fuel.

I checked that when I pulled the fuel pumps and looked at the socks

The fuel line that goes from the pump to the bulkhead is only like 2-3" long anyways....

[mattblancarte]

Well, you can try running like 60 psi of air through the fuel line. Maybe some rubber bits or something are stuck from the lines corroding internally.

Could be the pumps, though, as you are able to get 60 psi even for a bit. Would think that number wouldn't be hit with a blockage...

I'm sure you've already thought of this, though.

[Booztd 3]

Im going to try and run the fuel pumps with the car off, and send the outlet off the FPR to a bucket and try and run the regulator at 70psi of fuel pressure and see what happens....

[Booztd 3]

So tonight I had a few minutes to mess around with the car

I dialed my compressors regulator down to 30psi

With the car off, I turned the fuel pumps on, and hooked the compressor up to the FPR. The fuel pumps had no problem keeping a steady 70psi verified on the FRP gauge. I know this is just a static test, however I'm not sure how much more volume the pumps will flow when the car is eating up all that extra fuel...

Still stumped....

[matafied]

I ran into something crazy one time like this and it turned out to be a small hole in my fuel pump rubber hose. I took it out and inspected it and didn’t really see anything. Turns out after a couple of days of shotgunin parts the hole was only opening up when the fuel pressure was strong enough to expand the hose to relieve the pressure. Crazy

[Booztd 3]

I ran into something crazy one time like this and it turned out to be a small hole in my fuel pump rubber hose. I took it out and inspected it and didn’t really see anything. Turns out after a couple of days of shotgunin parts the hole was only opening up when the fuel pressure was strong enough to expand the hose to relieve the pressure. Crazy

I have seen this issue before, but it was a noticeable tear in the hose the last time I saw it......I'm going to pull them both back out tonigt and see what I find....

[Booztd 3]

Well tonight I did a test on these pumps using a tip I got from a friend

I took 2, 5-gallon buckets and I had a spare 5 gallons of E85. I filled one bucket up, and placed a fuel pump in the full bucket. I ran a line over to the empty bucket, and painted a mark on the empty one.



I then hooked the pump up and ran a stopwatch to see how long it would take each pump to fill up to the mark.

Between both pumps, one got to the mark an entire 60 seconds faster than the other one. That tells me theres a volume/flow issue with one, if not both. Since I have no OEM data to go off of.......

I believe I'm going to move forward with sourcing a big external pump tomorrow, at least that will remove the pumps from being the variable

I plan on just using an aeromotive eliminator. They're about half the price of the 'big' pumps and I havent really seen any failures associated with these. The eliminator is rated by aeromotive to flow 1400hp with Fuel Injected applications, which should give me a ceiling of around 900-1000rwhp....something I probably wont see with this car for at least a year or two. I plan on sticking around the 700rwhp mark until I have funds to move forward

The bonus is, the local speed shop has this pump and the recommended filters to go with it, in stock, and about 10% less than summit sells.....so i can get the stuff asap

[Darius]

Good detective work Sherlock Holmes!

Based on your experiment it sounds to me like one pump is not able to keep up with the pressure created by the other. As a result, it may be easier for fuel to back flow through the weaker pump versus being pressurized to 70 psi and trying to flow through the injectors and FPR.

You lucked out on the new Aeromotive pump. Buying locally is always a time bonus.

[Ramius83]

What pumps are you currently using and having issues with?????

[gawdzilla]

i believe he is using walbros. i've always heard of horror stories with dual pump setups and also walbros being inconsistent/slowly losing FP over time.

good thing you caught the issue. the aeromotive sounds like the way to go for your application. cheap insurance

[WhatsADSM]

i believe he is using walbros. i've always heard of horror stories with dual pump setups and also walbros being inconsistent/slowly losing FP over time.

good thing you caught the issue. the aeromotive sounds like the way to go for your application. cheap insurance

Yea walbro pumps are known for flaking out slowly over time.

However I'm pretty sure the OP is running twin Nissan z32 pumps.

When I finally redo my fuel system I am almost surely going with twin Bosch 044s.

[S14-NEO]

i can definately agree with (NOT) using walbros...those pumps have a very high failure rate...i have gone thru four of them until i decided to ditch them and go with a very reliable denso pump.. havent had any issue since..also when i was running a walbro it actualy failed while i was on the dyno if you can belive that...walbro pumps are absolute garbage....PERIOD!!!

[Booztd 3]

i quit using walbro's in high performance applications years ago

I've had 4 die on me........and its unlikely I'll ever use one again

That being said, I am currently running twin Z32 TT pumps. I have been running these for a few years at full battery voltage, so I'm wondering if that hasnt shortened their lifespan considerably.

On the stock Z32 setup, the car has a voltage regulator that only lets the fuel pump have 8V at idle, and something like 10-11 at cruise, and full voltage at WOT

[S14-NEO]

i quit using walbro's in high performance applications years ago

I've had 4 die on me........and its unlikely I'll ever use one again

That being said, I am currently running twin Z32 TT pumps. I have been running these for a few years at full battery voltage, so I'm wondering if that hasnt shortened their lifespan considerably.

On the stock Z32 setup, the car has a voltage regulator that only lets the fuel pump have 8V at idle, and something like 10-11 at cruise, and full voltage at WOT

its possible that it (may) have shorten the life span like you mentioned..did you buy them new or used...if you bought them new then that is definately puzzling for sure...but if you bought them used well then thats a different story all together... if you got them used they could have had a rough life , could be tired or just not been taken car of very well..

[Booztd 3]

They were def both used

I just looked up a single new OEM TT Fuel pump........293 dollars....

[S14-NEO]

you should seriously look into getting a set of denso pumps...they are well worth it and if im not mistaken they flow more fuel anyways than the stock TT pumps....the denso pumps are rated at 280liters per hour and if you ask me thats underated..hehehe

[gawdzilla]

what's the denso pump you're referring too? I always thought denso pump was synonymous with the supra tt pump, which is also a denso. either way, that's a reliable, quiet pump. just watch the amp draw on them and make sure your lid to pump wiring is high enough wire gauge. the supra denso is known to draw a lot of amperage. i know first hand that it will not flow it's full potential through stock s14 lid to pump wiring.

[S14-NEO]

thats exactly the same pump im running in my S14 and yes i had to reconfigure the power supply for the pump to work efficiently enough...

[Yellow4g63]

LoL same here too.

[Booztd 3]

Well I bit the bullet today....





Aeromotive Eliminator, 100micron pre-filter, 10micron post-filter

I did a faux sump on the tank. My tank is not anywhere near large enough on the bottom (its actually shaped like an upside down U (theres a hump to clear the driveshaft)

So on the passenger side, there was already a drain hole. I drilled it out to accept a -12 bulkhead fitting, and ran it to the fuel pump. So far there are no leaks, but I've only driven it around the block.

On the downside, it looks like you guys were right about the return, it doesnt appear the single -6 is going to work, as I could only dial my FPR down to like 55psi. I have one last provision on my FPR so I'm thinking about just adding a 2nd -6 return. I already have a -6 going to the top of one of my bulkheads because of the old fuel pump setup, so all I need to do is just run the line. The line going into the bulkhead is about -6 size, so I dont think I would benefit going to a -8 on the 2nd return since that bulkhead would just be a bottleneck. On the contrary I could just drill out that hole in the bulkhead and use an earls -8 bulkhead fitting.....

The pump isnt actually that much louder than my twin pumps running at battery voltage, I was surprised. I got a tip use the MSD rubber isolation mounts, however, the fuel pump sits really low where I mounted it on the car. Unfortunately, there was NO other place to mount it. Anywhere else it wouldnt have been bolted using all 4 bolts, or would have been RIGHT next to the exhaust....right now I've got about 4-4.5" of ground clearance on the pump, that kind of worries me....

[240z4u]

Andy, thanks for the post. I pulled one of my walbros because it was acting flaky. I have been contemplating running a pair of something pump wise. Seems it is smarter (and easier to plumb) a big single pump.

Would you mind sharing the vendors name who you bought the pump from? I would rather hand a guy in peoria my business vs. summit if I go this route.

Is sumping the tank absolutely needed in this type of application to keep the pump from cavitating during startup?

Thanks dude.

[Chaos the Xile]

Ouch thats a big bullet to bite but aleast your issue will be fixed! GL

[S14-NEO]

Well I bit the bullet today....





Aeromotive Eliminator, 100micron pre-filter, 10micron post-filter

I did a faux sump on the tank. My tank is not anywhere near large enough on the bottom (its actually shaped like an upside down U (theres a hump to clear the driveshaft)

So on the passenger side, there was already a drain hole. I drilled it out to accept a -12 bulkhead fitting, and ran it to the fuel pump. So far there are no leaks, but I've only driven it around the block.

On the downside, it looks like you guys were right about the return, it doesnt appear the single -6 is going to work, as I could only dial my FPR down to like 55psi. I have one last provision on my FPR so I'm thinking about just adding a 2nd -6 return. I already have a -6 going to the top of one of my bulkheads because of the old fuel pump setup, so all I need to do is just run the line. The line going into the bulkhead is about -6 size, so I dont think I would benefit going to a -8 on the 2nd return since that bulkhead would just be a bottleneck. On the contrary I could just drill out that hole in the bulkhead and use an earls -8 bulkhead fitting.....

The pump isnt actually that much louder than my twin pumps running at battery voltage, I was surprised. I got a tip use the MSD rubber isolation mounts, however, the fuel pump sits really low where I mounted it on the car. Unfortunately, there was NO other place to mount it. Anywhere else it wouldnt have been bolted using all 4 bolts, or would have been RIGHT next to the exhaust....right now I've got about 4-4.5" of ground clearance on the pump, that kind of worries me....

hey mani dont see a fuel pump controller in your little pile of goodies (which looks good by the way)...you may want to get the controller in order to get the optimum lifespan out of the pump...the reasoni say that is the pump isnt designed to run at full power all the time , it can get too hot and cause it to shorten its lifespan...Aeromotive make the controller and you may want to look into it.

[Booztd 3]

Well, I think I got it sorted today!

I didnt want to re-plum the WHOLE return system and by a new regulator if I didnt have to, so I started out simple, which involved a little reconfiguration in the fuel system.

I designed my system originally to have both sides of the fuel rail fed by a -8, and the single -6 return out the middle. The first thing I did was removed the -6 return to the regulator, I capped that off. Then I removed the 2nd -8 feed, and actually plumbed that to my regulator

After I did that, the pressure on the pump came down to 50psi, so I figured I was on the right track.

The next thing I did was re-do the fuel return into the fuel tank. I had originally just put a compression -6 fitting on the stock 5/16" line. I removed that hardline completely and installed a -8 bulkhead, and then adapted it to the -6 line going to it

After that, I checked the pump, voila, 40psi (where it was set originallly) At 20psi the car feels good again, fuel pressure stayed at 60psi, and it wasnt going lean anymore. We will see if the return can keep up once I wind it back up to 30psi of boost!

[Booztd 3]

Got the car out tonight and did some WOT pulls.......everything is in check.....car feels awesome.....

[Kevin.A]

Hey, when you put the car up, did you add fuel stabilizer?I have a 62 Triumph Herald that had a similar problem on a stock pump and when i took the pump apart to see how it works(natural curiosity) i noticed that the fuel had actually gelled in the pump itself.

[mattblancarte]

Got the car out tonight and did some WOT pulls.......everything is in check.....car feels awesome.....

[Booztd 3]

Negative

Never have used fuel stabilizer