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Lost fuel pressure. Pump runs but gauge reads 0psi


mr jdm

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Heres the fuel setup

 

Fuel cell -> external walbro pump -> filter-> fuel rail IN -> fuel rail OUT -> into Aeromotive FPR -> return line to cell

 

The car has been wired from scratch completely, its running a haltech e8.

 

Here is a video of it idling perfect

 

 

 

 

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Now, before you would get in the car, flip the ignition switch, flip the fuel pump switch, you would HEAR either the lines get pressurized or the AFPR do work. The gauge would read around 50, then SLOWLY drop to about 10-15

 

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Problem: I get into the car, I am flipping both switches, the pump is pumping, my fuel pressure gauge registers 50-60 psi for a SPLIT second the goes straight to 0 very fast. I was trying to start the car today and the car would not start, there is no pressure in the rail.

 

Any ideas for a solution or where to look?

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yea but before when it dropped to 10-15 psi, you heard loud "squeak", the lines getting pressure.

 

Now when it drops to 0 psi, there is no "squeak"

 

Theres no way its the FPR, I bought it brand new, it has had 5 starts on it and 1/2 mile of driving on it.

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If you can hear the pump running its the FPR. Even getting it new there's no telling how long it sat and in what conditions, the diaphram is prolly toast. Either way it only takes 5-10 mins to pull it apart and check.

 

Edit: That exhaust plumbing is crazy! Is it staying like that?

Edited by emoximuu
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Theres no way its the FPR, I bought it brand new, it has had 5 starts on it and 1/2 mile of driving on it.

 

Sorry, but that doesn't make it infallible. If you want to test it... pinch off the return line (back to the tank). If the fuel pressure comes up, the regulator is fubar. If the pressure stays down, you have a delivery problem... pump, pump wiring, plugged lines/filter, or a leak. Of course, this assumes the gauge is working correctly. And, Joel is correct, it should never have dropped to 10-15 psi.

 

And please please please post descriptive subject titles.

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I was working on the car today. Here is where I am at. When you install a haltech,it controls how long the fuel pump primes for. I have it set at 5 seconds, after 5 seconds it stops priming and when the car starts it turns on again. That is just a side note.

 

Today I bypassed the fuel filter, in hopes that it was clogged to the point where it was the problem. That is not the case

 

RTz, I tried doing what you suggested, pinching the line. THe pressure stayed down, however, I have only -8 stainless steel braided lines, so telling if I pinched the line completely down is kind of hard.

 

It just so happens I have an extra walbro laying around, I will try to install it tomorrow and see if that fixes the problem. If it doesn't I will be opening up the Aeromotive FPR

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After doing a little bit of research, it turns out that aeromotive fpr DO NOT hold fuel pressure after the pump is done priming. When my car was running great, I took it around the block twice, the first time around it drove great, the second time it got VERY slugish, I barely got back to my shop. At this point I realized I forgot to adjust the fuel pressure, and I am predicting it was running anywhere from 60-80psi.

 

Today, I hard wired the pump is stayed running the entire time, I made adjustments on the FPR and the gauge read accordingly.

 

I also pulled 4 spark plugs out, they are ALL full of carbon build up and you can smell gas on them. I'm pretty sure the only thing that happened was my motor flooded on my little 1/2 mile drive do not setting the pressure.

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After doing a little bit of research, it turns out that aeromotive fpr DO NOT hold fuel pressure after the pump is done priming.

 

Incorrect. A properly functioning FPR will hold pressure just fine after a prime. The loss in pressure after a prime is because there is no check valve stopping the fuel from back flowing through the pump. Or you have a leak.

 

But, now I'm beginning to understanding what you meant in your first post... the pressure drop to 10-15psi was occurring after the pump stopped running, correct?

 

 

 

Today, I hard wired the pump is stayed running the entire time, I made adjustments on the FPR and the gauge read accordingly.

 

So, you're saying the 0 pressure reading you were reporting was with the pump off? But when it's on, you can reach target pressure?

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Everything got fixed as of today. My motor was flooded from the 1/2 mile drive before setting fuel pressure.

 

Let me clear things up for people that find this as a search result.

 

Everything on my car is perfectly functioning.

 

If you have an Aeromotive Fuel pressure regulator, when you put your ignition to the ON position and your pump is priming, it will register fuel, when it STOPS pumping, it will drop to 0. It will NOT hold it.

 

If you want to set your fuel pressure, make sure the "prime" is bypassed and the fuel pump stays running as it would while the car is running. Set the pressure, then start your car.

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Bummer that you spent all that time only to find that the Aeromotive FPRs leak down quickly (edit - couldn't find the document to back this comment up)). If you look back at your original problem description, and the followups, it doesn't quite fit what you found. Just sayin', there's something odd.

 

I think that most people set fuel pressure with the fuel pump running.

 

You can also set fuel pressure with the engine running also. Disconnect the vacuum hose to the FPR, set the pressure with the engine running, then reconnect the hose. For future reference, easier than rigging something up to keep the pump running without the engine running.

 

It's all fun though. Good luck with the rest.

 

Edit - just saw RTz's post. The Aeromotive FPRs use a steel ball on an aluminum seat for the valve. It doesn't seal tightly, but it does regulate well. (or this one either).

Edited by NewZed
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The Aeromotive FPRs use a steel ball on an aluminum seat for the valve. It doesn't seal tightly, but it does regulate well. They note the issue in a technical bulletin on their web site also.

 

I'll fess up to my lack of experience with Aeromotive FPR's. But still... check valves are constructed by that description and they seal 'fine'. Why is this an issue for these regulators?

 

Also, the OP said "for a SPLIT second the goes straight to 0 very fast". If this is true with a functioning check valve, that seems like a pretty large shunt, doesn't it?

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I have spent some time in the past trying to figure out why my Aeromotive FPR leaked down quickly and eventually came across some information on the internet from an Aeromotive person, acknowledging that they leak down rapidly. I would guess they're saving money on machining costs.

 

I didn't understand the OP's first post either, in light of what was found in the end. Probably too many things going on at once, with new parts and all.

 

Edit - mr jdm beat me. I think that most FPRs will hold pressure. You're right jdm, the Aeromotive's work fine when the pump's on, but most OEM FPRs will hold pressure for weeks or months.

 

Edit #2 - the comments I saw from Aeromotive were similar to those in your second link mr jdm.

Edited by NewZed
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