Aeromotive Fuel Pressure Regulators Upgrade

NOTE: Proceed at your own risk. This is based on a 91 Diablo. I assume the same for 91-93, but may be the same for all 5.7 L. Check your own setup and ask questions if you have concerns before attempting this.

 

I saw this brand used on TopCarbon's old yellow Diablo. However, I will note some slight differences. Per the manual Fuel Pressure should be 2.5 bar or about 36 psi. The fuel pumps (and most fuel pumps) are 43.5 psi but difference flow rates and there is some loss through the system before the fuel rails. The stock 91 Diablo setup consists of two separate lines out of the fuel tank, each into pre filters, then fuel pumps, then post filters, then fuel rails before hitting the regulators. The regulators then have return lines which meet at a "T" fitting and then a SINGLE line runs back to the tank.

NOTE: this was the one difference on topcarbon's layout because each return had it's own line until somewhere close to the fuel tank. Not sure if this matters or was just a preference by his mechanic but I left the stock layout. Also, TC's mechanic chose a slightly different style FPR but to the best of my knowledge, they have the same psi range but are just different designs.

 

Parts List: (General note that there are some color options with different part numbers)

 

Aeromotive 13129 EFI Adjustable Fuel Pressure Bypass Regulator 30-70 PSI (Ebay $121 shipped each) - NEED 2

- NOTE: The fuel pressure regulator has 2 input ports, 1 return port, 1 gauge port, and 1 vacuum/breather port. This question was raised in old posts on whether one FPR could be utilized instead of 2. I can't see why that couldn't work, although you would not need plugs in that case but would either need 90 degree fittings or an assembly of fittings to meet the hoses to the fuel rails. Once you see pictures of the setup, you will understand why. BUT since no one confirmed that would work and this isn't incredibly expensive, I went ahead and went with the 2 FPR setup.

 

Aeromotive 15626 AN-06 Port Plug (Ebay $9.30 shipped each) - NEED 2

 

Aeromotive 15633 0-100 PSI Dry Fuel Pressure Gauge Chrome Bezel 1/8" NPT Male (Ebay $26 shipped each) - NEED 2

-NOTE: One of these came with fluid and one without. No idea which is better or if it matters. Part number was the same though...Also note that the FPRs come with a plug in the gauge port (see FPR picture) and you will need to remove these before installing the gauge.

 

Summit Racing® Hose Fittings SUM-220168 (Summit Racing $5 each) - NEED 4

-NOTE: This is a An-06 to 3/8" barbed hose fitting. I was able to get these to fit but I think the inner hose diameter for the fuel hoses is actual 5/16", which I didn't see offered by somewhere but if you wanted to get some of those too and try to see which fits better.

 

Fuel Hose Clamps - I got some from my local PepBoys for about $3 per pack of 4. NEED 4 or 1 Pack

 

The Plugs are used to block off one of the unused input ports on each FPR. Plugs and fittings come with O-rings but do NOT need sealant. Gauges do need sealant...teflon or other appropriate sealant. Plugs and fittings can be tightened with a 19mm wrench.

 

 

BEFORE you remove the old FPRs, you need to get rid of the fuel pressure in the system. Easiest way is to turn the car on and then pull the couple fuses in the compartment behind storage behind the passenger seat. This stops power to the fuel pumps and relieves most of the pressure. PLEASE check your manual or ensure you are pulling the right fuses if this is not an early Diablo. Double and triple check.

 

 

REMOVE stock FPR:

Remove vacuum/breather hoses (tiny hoses). Place paper towels or rags under the hose ends to catch the fuel.I used some pliers to squish the clamps to loosen in order to pull the lines off the FPRs. May be a small puff with the remaining fuel pressure once the first hose comes off. Each FPR is held onto a metal bar by a small allen head screw so remove those in order to pull off the FPRs.

 

Slide NEW fuel hose clamps onto the hose end and then push the fittings into the hoses. Once they are in far enough, tighten down the new clamps. How you mount the FPRs is up to you. Ensure everything is tightened up. Then put the fuses back in and turn the key to the accessory on position (DO NOT START IT). This should allow fuel pressure to build and you can use the allen head to adjust the fuel pressure on each gauge to be ~36 psi. If pressure does not build, may need to turn key off and wait a minute and then turn key back to accessory on position. See instructions that come with FPRs.

 

Tomorrow I will add more pictures of my actual set up. Since I have an exhaust and intakes, I may set my FPRs at 37 psi.

NOTE: Proceed at your own risk. This is based on a 91 Diablo. I assume the same for 91-93, but may be the same for all 5.7 L. Check your own setup and ask questions if you have concerns before attempting this.

 

I saw this brand used on TopCarbon's old yellow Diablo. However, I will note some slight differences. Per the manual Fuel Pressure should be 2.5 bar or about 36 psi. The fuel pumps (and most fuel pumps) are 43.5 psi but difference flow rates and there is some loss through the system before the fuel rails. The stock 91 Diablo setup consists of two separate lines out of the fuel tank, each into pre filters, then fuel pumps, then post filters, then fuel rails before hitting the regulators. The regulators then have return lines which meet at a "T" fitting and then a SINGLE line runs back to the tank.

NOTE: this was the one difference on topcarbon's layout because each return had it's own line until somewhere close to the fuel tank. Not sure if this matters or was just a preference by his mechanic but I left the stock layout. Also, TC's mechanic chose a slightly different style FPR but to the best of my knowledge, they have the same psi range but are just different designs.

 

Parts List: (General note that there are some color options with different part numbers)

 

Aeromotive 13129 EFI Adjustable Fuel Pressure Bypass Regulator 30-70 PSI (Ebay $121 shipped each) - NEED 2

- NOTE: The fuel pressure regulator has 2 input ports, 1 return port, 1 gauge port, and 1 vacuum/breather port. This question was raised in old posts on whether one FPR could be utilized instead of 2. I can't see why that couldn't work, although you would not need plugs in that case but would either need 90 degree fittings or an assembly of fittings to meet the hoses to the fuel rails. Once you see pictures of the setup, you will understand why. BUT since no one confirmed that would work and this isn't incredibly expensive, I went ahead and went with the 2 FPR setup.

 

Aeromotive 15626 AN-06 Port Plug (Ebay $9.30 shipped each) - NEED 2

 

Aeromotive 15633 0-100 PSI Dry Fuel Pressure Gauge Chrome Bezel 1/8" NPT Male (Ebay $26 shipped each) - NEED 2

-NOTE: One of these came with fluid and one without. No idea which is better or if it matters. Part number was the same though...Also note that the FPRs come with a plug in the gauge port (see FPR picture) and you will need to remove these before installing the gauge.

 

Summit Racing® Hose Fittings SUM-220168 (Summit Racing $5 each) - NEED 4

-NOTE: This is a An-06 to 3/8" barbed hose fitting. I was able to get these to fit but I think the inner hose diameter for the fuel hoses is actual 5/16", which I didn't see offered by somewhere but if you wanted to get some of those too and try to see which fits better.

 

Fuel Hose Clamps - I got some from my local PepBoys for about $3 per pack of 4. NEED 4 or 1 Pack

 

The Plugs are used to block off one of the unused input ports on each FPR. Plugs and fittings come with O-rings but do NOT need sealant. Gauges do need sealant...teflon or other appropriate sealant. Plugs and fittings can be tightened with a 19mm wrench.

 

 

BEFORE you remove the old FPRs, you need to get rid of the fuel pressure in the system. Easiest way is to turn the car on and then pull the couple fuses in the compartment behind storage behind the passenger seat. This stops power to the fuel pumps and relieves most of the pressure. PLEASE check your manual or ensure you are pulling the right fuses if this is not an early Diablo. Double and triple check.

 

 

REMOVE stock FPR:

Remove vacuum/breather hoses (tiny hoses). Place paper towels or rags under the hose ends to catch the fuel.I used some pliers to squish the clamps to loosen in order to pull the lines off the FPRs. May be a small puff with the remaining fuel pressure once the first hose comes off. Each FPR is held onto a metal bar by a small allen head screw so remove those in order to pull off the FPRs.

 

Slide NEW fuel hose clamps onto the hose end and then push the fittings into the hoses. Once they are in far enough, tighten down the new clamps. How you mount the FPRs is up to you. Ensure everything is tightened up. Then put the fuses back in and turn the key to the accessory on position (DO NOT START IT). This should allow fuel pressure to build and you can use the allen head to adjust the fuel pressure on each gauge to be ~36 psi. If pressure does not build, may need to turn key off and wait a minute and then turn key back to accessory on position. See instructions that come with FPRs.

 

Tomorrow I will add more pictures of my actual set up. Since I have an exhaust and intakes, I may set my FPRs at 37 psi.

Chipster,

 

The Aeromotive 15633 fuel pressure gauges that you have are supposed to be liquid filled. Perhaps the little vent on the top of the gauge opened and the liquid leaked out. I'm not sure how much needle fluctuation will occur on the Diablo when it's running, but the liquid is in the gauge to dampen that fluctuation and provide a steadier reading. The disadvantage of a liquid filled gauge over a dry gauge is the pressure reading on the liquid filled gauge will be affected by temperature in the engine compartment. That is why the manufacturer provides the external vent on top of the gauge. Once you have it mounted with the vent at the top (so the liquid doesn't leak out), lift up on the stem to equalize the pressure, then push it back down and take your readings. Keep us posted on how it goes.

Very interesting, thanks. The one gauge was dry but the vent was closed. They are held down by a strap. Gauges are almost horizontal, so I'll have to be careful bleeding. Will update this thread once I get that done.

I love following you DIY threads! I can do the same thing on my DD but it isn't nearly as exciting as following along on your Diablo.

I love following you DIY threads! I can do the same thing on my DD but it isn't nearly as exciting as following along on your Diablo.

 

I haven't finished so I don't actually have proof yet that any of you should trust me with this but hopefully lol. Thanks man. Just trying to share in case someone else could benefit from it

Chipster

Thanks for sharing. Hopefully the weather will break soon and you will get a chance to enjoy your bull.

I haven't finished so I don't actually have proof yet that any of you should trust me with this but hopefully lol. Thanks man. Just trying to share in case someone else could benefit from it

 

 

Haha I totally understand but you try! I might not be pulling the engine from my civic anytime soon but these type of threads have given me the encouragement to do minor stuff like discs/pads, 02 Sensors and spark plugs.

 

I ALMOST attempted a head gasket/water pump/timing belt replacement in December of 2013 but it was way to cold out for that and my garage wasn't set up to handle the replacement work yet.

 

Keep it up!

 

It has been done before.

 

http://www.lambopower.com/forum/index.php?showtopic=39720

Chipster

Thanks for sharing. Hopefully the weather will break soon and you will get a chance to enjoy your bull.

 

Thanks! Yeah, looking forward to spring! Caught a cold so haven't finished up doing this upgrade yet.

 

Haha I totally understand but you try! I might not be pulling the engine from my civic anytime soon but these type of threads have given me the encouragement to do minor stuff like discs/pads, 02 Sensors and spark plugs.

 

I ALMOST attempted a head gasket/water pump/timing belt replacement in December of 2013 but it was way to cold out for that and my garage wasn't set up to handle the replacement work yet.

 

Keep it up!

 

My dad just got a lift and unfortunately he got the standard size so the Diablo is too wide!! I could probably do some work around to get it on there but that would have been handy for doing some of these projects. I try to do all the work I can.

 

It has been done before.

 

http://www.lambopower.com/forum/index.php?showtopic=39720

 

True! But there weren't any details on the parts numbers required or anything like that but I definitely looked at that as a source and that's why I mentioned topcarbons car in the first post. I think cannonball or something like that owns that yellow 91 now but I'm not sure if the Aeromotive setup was still on there.

Looking forward to pictures and further details of the install.

 

Looking at the original thread by TopCarbon, everything looked top notch except his mechanic used worm and roller clamps to connect a rubber coupling section to the original fuel rails, there are definitely other options (cleaner and safer) using a combination of metric / AN fittings from Earls or Aeroquip.

Looking forward to pictures and further details of the install.

 

Looking at the original thread by TopCarbon, everything looked top notch except his mechanic used worm and roller clamps to connect a rubber coupling section to the original fuel rails, there are definitely other options (cleaner and safer) using a combination of metric / AN fittings from Earls or Aeroquip.

 

My setup will be the same as stock, except instead of the crush type clamps, I used the adjustable screw type clamps. I assume that it should be fine since it has made it like this for 20+ years. Also since this is still around stock fuel pressure, I'm not too worried about it. Since there are multiple barbs on the hose fitting adapter, it's good chances of getting a solid seal. But if I notice any leaks once I get fuel pressure, then I will change out with all adapters. Honestly I thought about doing that from the start and I could have sworn I found a post by someone before where they said what thread sizing was needed to mate up to the fuel rails but when I looked back, I couldn't find that post again. Hopefully, I'll have an update this weekend!

So it was a little warmer today, popped the fuses back in and turned the key to the accessory on position and the fluid gauge jumped up to about 20 I think. Dry gauge too but then the dry gauge dropped back down. These are 30-70 psi FPRs so I was assuming I'd be in that range. Not smelling fuel noticing any leaks. Wanted to post these details and see what people think before I actually crank the engine.

 

 

Looks good. Can't tell from your pictures, but were you able to use the existing mounting brackets (the twisted pieces of flat steel) for your new regulators or did you have to make something new?

Fuel_Pressure_Regulator.PDF

 

Here's the relevant page from my '91-'93 service manual. It may be of use to you regarding the system fuel pressures at the various vacuum settings.

Fuel_Pressure_Regulator.PDF

 

Here's the relevant page from my '91-'93 service manual. It may be of use to you regarding the system fuel pressures at the various vacuum settings.

 

Thanks but shouldn't I have pressure permanently on the gauges or should I crank it up and then adjust? I know the pressure can bleed off when the car is shut off and Aeromotive even says that is likely. Based on previous threads on here...supposedly it should be at 36psi cold and low 30s at operating temp. I could try to crank it up and then adjust them but I don't know if what I'm currently seeing means issues with some or both of the gauges.

 

I have not decided how to mount them. Right now they stay fairly well based on the hoses. The clamp bolts are each sitting on the mounting brackets but I'll figure out some way to secure them for now.

I'm not sure what your static pressure should be with the engine off and the key in the accessory on position. The ECU's should start the pumps momentarily to pressurize the fuel rail, which is likely the 20psi reading that you saw on the gauges. At this point, there will not be any vacuum on the FPR's because you don't have the engine running. The 20psi seems a little low to me since you said these new FPR's are 30 to 70 psi, but perhaps the pumps weren't on long enough.

 

To truly adjust the FPR's, the pumps will need to be running (like it states in steps 3 & 4 of the fuel pump delivery check) and you'll need a handheld vacuum pump to check the fuel pressures at the different vacuum levels that you apply with the vacuum pump. Doing the "bar to psi" conversions, from the table it looks like from ~26psi @ 600mm/Hg and ~33psi @ 200mm/Hg are the range of pressures you're after.

 

I'm kind of surprised that your pressures went back to 0 so quickly. The manual seems to imply that 1 bar (14.5psi) of pressure should remain on the system for about an hour.

I'll look at it more tomorrow. I had let the key on and cycled off and back on with a minute delay like the directions stated from Aeromotive. The gauge with fluid seemed to hold pressure much better than the dry gauge.

From my experience installing these Aeromotive FPRs on other fuel injected cars, you need 35-40psi (min.) to start the car, so you need to adjust them accordingly.

Ok, so I went ahead and cranked up the car. Both gauges went up to about 60 psi lol, so I shut down and adjust the pressure down much lower and then was floating about 40 psi but the car was acting like it wasn't getting fuel and RPMs dropped very low and idled there. So I finally changed the pressure so the gauges were reading 30 psi and the car was happy with that. Took it out for about 25 mile drive and got some new fuel in there. Ran great! No leaks, felt smoother too. Not exactly hot out...about 60...but all my temps were pretty solid too. Felt great to open it up on the interstate and I forgot how much attention it gets!

 

EDIT: In the future, if I need to replace fuel pumps again, I think I will try to figure out some different pumps with a higher flow rate.

Great! Glad you're back up and running again.

Great! Glad you're back up and running again.

 

Thanks and thanks for the help!

No problem. Enjoy it, it's Spring Break!

To further this, does anyone have suggestions for the easiest way to check my air fuel ratios for each bank? I don't want to cut into the exhaust and weld in a new bung for another sensor.

I use a clamp on my tailpipe and hook it to my Innovate LM1, the clamp is specifically designed for the LM1 lambda probe.

 

Thanks, I was looking at some of the innovate stuff. Basically, I had gotten the gauges reading similar pressures last Sunday and the engine seemed happy and drove great. Fast forward to yesterday, I cranked it up and it shut off. Pressures were showing above 40psi. Which is too much for the fuel pumps of course and that's why the engine shut out. Soooo for one thing, comparing the set up top carbon had compared to mine with 1 return line at a T fitting, I'm wondering if that some how links the FPRs so that one FPR is trying to over ride the other and maybe they are actually at different fuel pressures. Not sure if that makes any sense. I adjusted them again and it ran fine. I guess I will see how it does when I start it up this weekend. But I figure it would be good to check the A/F ratio but didn't want to be modifying exhaust pipes. I do find it surprising that there are all these adapters and extensions for O2 sensors but apparently no adapters that would allow for 2 sensors...one for the normal O2 to feed the ECU and then another for an A/F gauge. Can't find anything like that. I'm catless so the exhaust tip like you mention should work fine. Thanks!