Quick Fuel Diagnosis Anyone? (Coyote Swap)

Werecow · Nov 14, 2020

What size are the lines as it hits the fuel filter? I mean it may be a stupid question, but is it the stock fuel filter and stock line from the filter to the tank? If so that in itself may be your restriction, as that's a 5/16 line and would cause your fuel pressure to show higher because of the smaller line there. Also the return line in the factory fuel hanger is only a 5/16, dunno if it'll cause it that close to where it dumps the fuel or not?? Like I said may be stupid questions but just my $0.02, trying not to overlook anything...

ForeverDriven · Nov 14, 2020

Werecow said:
What size are the lines as it hits the fuel filter? I mean it may be a stupid question, but is it the stock fuel filter and stock line from the filter to the tank? If so that in itself may be your restriction, as that's a 5/16 line and would cause your fuel pressure to show higher because of the smaller line there. Also the return line in the factory fuel hanger is only a 5/16, dunno if it'll cause it that close to where it dumps the fuel or not?? Like I said may be stupid questions but just my $0.02, trying not to overlook anything...

Yeah its pretty much all stock lines.

Werecow · Nov 14, 2020

white95 said:
Michael is right. Start with the basics before you make sweeping changes.

Agree with @white95 100% basic troubleshooting is K. I. S. S. Keep it simple stupid! It's always the simple things we overlook and it all goes back to simple troubleshooting steps...

Werecow · Nov 14, 2020

That may be the easiest, well not easiest, but the best place to start then if the rest of the lines are -6, start from the last one on the return side and replace the filter and rest to the fuel hanger. They do have a adapter from a -6 to the fitting on the fuel hanger I believe and that'll have the rest of the return side finished.. Unless I misunderstood part of what you were saying earlier...

apsmith49921 · Nov 14, 2020

Why would the stock lines be too small? People boost 2v cars all the time with out changing the fuel lines. 400hp on stock lines should be fine unless they are plugged up. I suggest checking the fuel filter.

I watched a gt500 ping pretty good on the dyno because it had a dented fuel filter from when it was wrecked. (Salvage rebuild)

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white95 · Nov 14, 2020

apsmith49921 said:
Why would the stock lines be too small? People boost 2v cars all the time with out changing the fuel lines. 400hp on stock lines should be fine unless they are plugged up. I suggest checking the fuel filter.

I watched a gt500 ping pretty good on the dyno because it had a dented fuel filter from when it was wrecked. (Salvage rebuild)

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Be that as it may, it’s safer to advise a proven upgrade then to say it’ll work as is and lead to a potential disaster.

apsmith49921 · Nov 14, 2020

I dont disagree at all. Having more fuel available than you need is nice. However I would be hard pressed to think it's the root cause

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ttocs · Nov 14, 2020

maybe I a

ForeverDriven said:
I have it at 55 psi with vac line

someone correct me if I am wrong but I thought you set the fuel pressure with out the vac line on? I thought that is what I read to do on mine and what I did but not sure if I am wrong or a different system again.

Werecow · Nov 15, 2020

ttocs said:
maybe I a

someone correct me if I am wrong but I thought you set the fuel pressure with out the vac line on? I thought that is what I read to do on mine and what I did but not sure if I am wrong or a different system again.

Maybe so on your setup but remember you have a boosted application, your fuel pressure is referenced differently than a NA application because of this.

lwarrior1016 · Nov 15, 2020

Aeromotive suggests setting base fuel pressure with the vacuum hose off. That being said, I think was PBH (correct me if I’m wrong @white95) that said the coyote does best with fuel pressure set at constant 58psi. My regulator is set to 60 psi and does not have a vacuum reference at all.

ForeverDriven · Nov 15, 2020

All very nice replies, thank you all for the ideas! Apsmith read my mind, I never thought lines would be a problem because many 2v guys can run 600whp on stock lines.
It's worth noting that I don't think I have any leaks because I never smell fuel, but I haven't actually let the car run and *checked* all the AN connections I made. May be worth it. I tried rigging up a little NPI extension hose so I could see my fuel pressure gauge as I drove but that broke pretty quick.

But on another note, I'll also reset my fuel pressure to 58 PSI without vac reference. For the peeps here talking from coyote experience, did you really just plug all the vacuum hoses and not use the regulator reference? I did that when I first got it to run but it continued to randomly die as I drove. Now I suppose that might have actually been my weak old pump causing that and I don't actually need any vacuum references. Still, the way I have it set up now shouldn't be causing any issues so I don't wanna jump the gun and eliminate the only thing possibly keeping me from blowing it up lol.

I'll keep it simple for now, grab a K&N filter and install it this week. Also reset that fuel pressure.

white95 · Nov 15, 2020

One thing that I need to remember is the fact I’m running Holley EFI and it’s a different animal than the FRPP control pack. The only two items connected to vacuum are MAP sensor and the HVAC.

You really should do as your install literature suggests and change that fuel filter out.

ForeverDriven · Nov 29, 2020

Alright, for those of you still interested, I made "progress."

I replaced the fuel filter and reset the fuel pressure with the line clamped. It definitely ran better, and I could randomly accelerate full throttle too. However, it would also randomly cut out like before still, and I was randomly losing fuel pressure altogether.

The previous owner installed a second external fuel pump that was rated at 35 gph (roughly 135 lph) which I had taken out, simply reclamped the lines back to stock config. HOWEVER, there was still the wiring he did. The pump ran a second set of wires up to the trunk, and I'm gonna do my best to explain this setup:

MY fuel pump positive from the coyote pack goes to the inertia switch, which then puts out a purple wire. I do not know where this purple wire is supposed to go, but on the opposite side of the trunk, the guy found the wire and spliced into it, connecting another wire to power a Hella Relay (4RD 960 388) which had a ground and two other outputs. One yellow wire to the external pump and another to the internal pump.

If you understand what I described, then you should understand what I was thinking when I decided to simply connect the original power wire to the fuel pump wire and call it good. I cut off all other connections to the relay in the trunk and I have 11.37v all the way to the pump wire. It ran for a few minutes, but the fuel gauge was very jumpy until it finally cut out. I now have no pressure at all. I can hear a slight hum from the fuel pump but I do not build pressure. I reconnected everything to the old setup and still nothing.

Perhaps the relay served as the pump's ground, but that doesn't make sense since there was no ground wire for that pump coming into the trunk, just the power wire going out. I honestly have no idea at this point. I'm hoping that the new pump isn't garbage, but we'll have to see. I want to hear everybody's ideas for now.

ttocs · Nov 29, 2020

is your battery reading 11.5v when your reading 11.3 on the pump wires?

ForeverDriven · Dec 1, 2020

ttocs said:
is your battery reading 11.5v when your reading 11.3 on the pump wires?

Went out and tested this yesterday and my multimeter ran 10.93v on both battery and pump wire, a little low but probably from all the times I tried to crank it over.
However, it just started up again today perfectly fine?!? First key switch only got me half pressure but second switch went all the way and it ran fine while I got it in the driveway. I'm at such a loss for what it is.
The fuel pressure does fluctuate as I give it gas which I'm guessing is normal as well, but I just have no clue

ttocs · Dec 1, 2020

well lets start with the obvious that the battery is at the very least in need of a good charge or possibly being replaced. IF your starting at 11.5 before cranking your probably going down less than 10v during cranking and that will effect fuel pressure and the ignition will be having problems as well. Try something stupid and get out some jumper cables and either another battery if you have one or another car and see if it fires up better with enough voltage for a change.

ForeverDriven · Dec 1, 2020

ttocs said:
well lets start with the obvious that the battery is at the very least in need of a good charge or possibly being replaced. IF your starting at 11.5 before cranking your probably going down less than 10v during cranking and that will effect fuel pressure and the ignition will be having problems as well. Try something stupid and get out some jumper cables and either another battery if you have one or another car and see if it fires up better with enough voltage for a change.

I'll try this sometime today or tomorrow when I can. I'm not too sure because it fired up like normal again today, and the original issue was the car dying randomly while driving, so the battery was being charged just fine. So hooking up jumper cables may not help since I have to drive it to see if it dies lol

ForeverDriven · Dec 3, 2020

No avail. The car is still starting fine and getting power, issue becomes apparent after startup. I'm gonna post a short video of whats happening with none of the extra wires hooked up

ForeverDriven · Dec 3, 2020

This is with the entire aftermarket wiring setup (that other guy did) completely disconnected. On startup, it will stay solid like it should for about 30 seconds.

My problem is that with the wires connected, it doesn't do this (pressure stays constant) but it will still die after a while. This makes me think its wiring and not a bad pump but I just can't figure out what.

Since I sent my fuel pump wire from the control pack straight to the inertia switch, could that be a problem? Does some sort of relay or something need to be between the power source and the pump?