Cranks but no start; no fuel pressure

[TheFleshRocket]

I was in the process of bleeding the brakes on my Cobra following rebuilding the front calipers (plus new pads and rotors) and was having some trouble getting all of the air out. One of the recommendations I saw was for pumping the brakes with the engine on, so I did so. With the car idling (I think it was cold but don't remember for sure), I pumped the brakes hard several times. On each brake pedal depress, the car shuddered and the idle dropped to around 500 RPM, but it recovered each time I released the brake.

I then went for a couple-mile test drive. The car ran fine, but the brakes were still a little mushy. I rebled the reservoir, the rears, and then the fronts, and finally had a hard pedal. When I tried to start my Cobra to go out for another test drive, it cranked but would not start.

I hooked up my OBD2 gauges (little Bluetooth OBD2 adapter, using the OBD Fusion app on an Amazon Fire tablet), and it showed 0 PSI of fuel pressure. I immediately assumed the FRPS, as it had gone out on me a little over a year prior with the same symptoms. I got a new sensor and installed it, but was still seeing 0 PSI. I checked the fuse in the VMP fuel pump booster and it's good.

When I turn the key to "on", the fuel pump audibly cycles, so I assume it's getting power.

I did a PPRV delete using the LFP kit several months back. I bought a second set of clamps, and double-clamped the three hoses at each end, and made sure that they were plenty tight, so I don't think it's likely that a hose blew off.

I would have already pulled the tank but it's 3/4 full and it'll be kind of a pain to get it siphoned down low enough so that the tank isn't too heavy.

Is there anything else I can / should check before siphoning fuel and dropping the tank?

(My Cobra has a TVS, 60# injectors, VMP MAF, VMP pump booster, LFP PPRV delete, and a few other things I'm forgetting.)

 

[dumbstixlars]

I have heard of people getting new FRPS that are bad out of the box, that might still be your problem. You pull the vacuum hose to see if it has fuel in it?

 

[TheFleshRocket]

I haven't checked the vacuum hose, but I will at lunch. I assume that if an FRPS fails, it can allow some fuel to be sucked into the vacuum hose?

 

[TheFleshRocket]

No fuel in the vacuum hose. I tried starting it again. It cranked and caught, coughed and sputter at 300ish RPM, surged to 900 or so, then coughed and sputtered, surged, sputtered, and died. Left a nice cloud of fuel behind the car in my garage.

 

[hotcobra03]

when I had my car down for head..I needed the fuel..

I jumped pump at rear bumper to straight 12v..

than behind passenger head..took line off at old school white pull tab..connected hose from there to can..

this only takes a few mins,

it will confirm fuel coming by pump only..

 

[cj428mach]

sounds like the hoses blew off.

 

[TheFleshRocket]

when I had my car down for head..I needed the fuel..
I jumped pump at rear bumper to straight 12v..

What wire do I supply 12V to, and where's it located? Thanks!

 

[hotcobra03]

c463.. connector is attached to rear bumper..if not moved from last tank drop..find wire coming from top of tank toward bumper..should see it.

unplug..run jumper to just tank.

6/7

 

[hotcobra03]

14 is size of wires..

 

[TheFleshRocket]

Thanks for posting the diagram, but I’m having trouble deciphering it compared to the actual connector. It is still attached to the bumper (I try to be good about putting things back where I found them). Can you help me with specifically which lead gets 12v and which gets ground? (I have a spare old motorcycle battery that holds a charge and am gonna use that to power the pump.) thanks again!

 

[hotcobra03]

Thanks for posting the diagram, but I’m having trouble deciphering it compared to the actual connector. It is still attached to the bumper (I try to be good about putting things back where I found them). Can you help me with specifically which lead gets 12v and which gets ground? (I have a spare old motorcycle battery that holds a charge and am gonna use that to power the pump.) thanks again!

View attachment 1457951

look at pic..
brown/pink wire..pin #6..
12v..

pin#7 red/black..is ground..

sorry no pc to be able to post pic of connector..

follow wire colors of main harness.
to pin location..

I can' say if colors follow thru on tank harness

 

[hotcobra03]

try quick search..I had posted this a couple times..

since new format..I had lost every thing I've saved..

 

[jjk23]

OP,

You are doing the right thing by checking the easy things first.
You mentioned observing zero fuel pressure using your OBD app + tablet.
Did you check fuel pressure before and after key-up?
[I assume your OBD app can read live data.]
If you have not checked fuel pressure in both cases, I would do so.
[If you can hear the pumps priming following key-up, the pumps are getting power.]

If your tool cannot read live data and you are still on the stock fuel rails, you could pick up a simple fuel pressure test kit. The Schrader valve is located on the passenger-side fuel rail.

The last items to check before dropping the tank would be your FPDM and connections at the voltage booster. If you have a spare FPDM or have a friend that has one, try it out.

The absolute last thing before dropping the tank:
Your previous comment regarding the "cloud of fuel" makes me curious about your new FRPS.
Go back to the parts store and exchange the FRPS for another one.
Install the new FRPS and make sure your battery is completely charged before attempting to start the car. It would not hurt to pull all the spark plugs and let the car sit for an hour or two [just make sure all the fuel is out of the cylinders].
If this lands you in the same position as before, be prepared to drop the tank. Luckily, it sounds like you have had the tank down before. I would just get one or two friends and some Pig Mat.

Did the PPRV delete kit from LFP use worm-gear clamps or Oetiker clamps?
I recommend installing some Oetiker clamps if you are given the chance.
They are easy to install and are very resilient against vibration.

You will get this sorted out, just may take a day or two.
Good luck!

 

[TheFleshRocket]

Due to personal / family issues, working on my Cobra has been on hold, until now, four months later. It's finally nice outside and I'm ready to enjoy the Cobra a bit.

[If you can hear the pumps priming following key-up, the pumps are getting power.]
If your tool cannot read live data and you are still on the stock fuel rails, you could pick up a simple fuel pressure test kit. The Schrader valve is located on the passenger-side fuel rail.

My OBD2 reader does show live data, and fuel pressure stays at 0 psi with key off, key on, or cranking. I also picked up a fuel pressure test kit and it confirms 0 psi at the Schraeder valve under those conditions.

Your previous comment regarding the "cloud of fuel" makes me curious about your new FRPS.
Go back to the parts store and exchange the FRPS for another one.
Install the new FRPS and make sure your battery is completely charged before attempting to start the car. It would not hurt to pull all the spark plugs and let the car sit for an hour or two [just make sure all the fuel is out of the cylinders].

I'll pick up a new FRPS this afternoon. Since the car has sat for four months, I'm sure the cylinders are dry.

The last items to check before dropping the tank would be your FPDM and connections at the voltage booster. If you have a spare FPDM or have a friend that has one, try it out.

The auto parts store also has an FPDM in stock, so I'll get one of those as well.

Did the PPRV delete kit from LFP use worm-gear clamps or Oetiker clamps?
I recommend installing some Oetiker clamps if you are given the chance.
They are easy to install and are very resilient against vibration.

I'll post pics in my next reply. I used worm gear and .. not sure what the other style of clamps are called. I put two clamps on each end of each of the three hoses--one of each type.

 

[TheFleshRocket]

Here are pics of how I installed the hoses and clamps.

If one of the fuel lines blew off, wouldn't the pump stay running continuously because it would assume that there is no fuel pressure and therefore keep trying to achieve that pressure?

 

[TheFleshRocket]

Another FRPS did not fix the issue. I’d cycle the key at least three times, then cranked the engine. It would fire, rev to 1500 or so, but die instantly. The gauge on the fuel rail never budged from zero.

 

[procharger]

I believe the hose came off your pumps, due to the BAP pressure flowing thru 5/16 hose will have some back pressure, also stock pump do not have barbs to secure the hoses and are slightly tapered. I believe you should have 3/8 hoses, as far as keeping the hoses on stock pump it's a gamble. I change pumps to avoid headaches, I have seen a lot of setup that use adhesive on the hose to pump.

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[SVTdreamin04]

I believe the hose came off your pumps, due to the BAP pressure flowing thru 5/16 hose will have some back pressure, also stock pump do not have barbs to secure the hoses and are slightly tapered. I believe you should have 3/8 hoses, as far as keeping the hoses on stock pump it's a gamble. I change pumps to avoid headaches, I have seen a lot of setup that use adhesive on the hose to pump.

Sent from my [device_name] using the svtperformance.com mobile app

Agreed. Rather common for hoses to come off on these setups. Can you hear sloshing around inside of the tank when the pumps are running? Can you hear the pumps running?


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[TheFleshRocket]

Agreed. Rather common for hoses to come off on these setups. Can you hear sloshing around inside of the tank when the pumps are running? Can you hear the pumps running?

The pumps come on for about one second when the key is cycled on, then shut off. If a hose had blown off, would the pumps run continuously, futilely attempting to build fuel pressure?

 

[SVTdreamin04]

Yes. Correct.


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