Aloha all,
Im attempting to get to C3 project started and having a tough time hopeing someone has ran into this issue.
once the key is turned into the ON position, the fuel pump turns on and the pressure gauge reads 43 PSI.for 3 seconds then the pumps stops and the pressure immediately drops to zero. During cranking
The pressure does not go up, it remains at zero.
I am getting good spark from my MSD 6AL. Wires are in the correct order and the timing is set to TDC..
the fuel pum. Regulator are both FAST EFI from a kit.

I have read some other messages with no luck
also wondering if I have the vacvacuum in the wrong spot (yet still same issue if it's hooked up or not.)

Please remember this is a Fast EFI system , it operates different from a carb so looking for those who have FAST experience.
thanks for any replies.
V/r,
Karp

 

If the Fast system is some what like a GM EFI system if the ECM doesn't see crank rotation it turns off the fuel pump.
So are you losing/don't have crank sensor signal?
Other than that I would contact Fast.

 

OK, you have two problems.

1) If the fuel PSI is immediately dropping to zero after the pump primes, you have a leak somewhere. You need to solve that problem first.

2) After the fuel pump primes at key on, the fuel pump signal stays off until the ECU determines that the engine is running. That is determined by the "Crank to Run Mode RPM" setting. Too high and the ECU will never turn the pump on, too low and you will transition to run mode before the engine lights off.

I have been using FAST XFI for over a decade know. My prime is set to 12 seconds and my Crank to Run RPM is 400. Works great for me.

Find the fuel leak and bump the prime time. But fix the leak first since that is dangerous situation.

 

Aloha All,

Thanks for the replies, I'll start digging into those issues.

1) Fuel Leak: Thankfully I have not detected any external leaks, which means it either going back into the tank via the return line or worst, its dumping it into the piston bore (yikes). I don't think its dumping as I don't smell gas
Hopefully It is a bad fuel regulator? I'll look into that:
What if the return line and fuel line were hooked up backwards? I didn't install the system: I'll double check the plumbing is correct, I think I can hear the fuel being put back in the tank but not sure, defiantly can hear the pump and fluid flowing.

2) I'll have to go through the diagrams and make sure I hooked up the RPM module correctly.

Is the vacuum hose in the correct location? I see on the bottom of the EFI Carb there is the smaller 3/8" one on the front right and a larger one (two actually) on the read of the EFI Carb.
I hooked the regulator vacuum up to the smaller one since they are roughly the same size. (trying to curb off the next Doh moment)

Thanks for the helpful inputs.
V/r,
Karp

 

If there is no external leak. The most likely culprit is the check valve in the pump. I've seen a number of aftermarket pumps sold under various names come through with bad check valves.
(Replace Pump).
This actually won't hurt a thing when running, as the pump runs full time when running. But can certainly give you start issues.
Also. I'm no expert on MSD systems. But your second issue is certainly a matter of not getting a tach signal.

 

Ok, let’s do a little more diagnosis.

- The only vacuum signal you need connected to start the engine is from manifold vacuum to the MAP sensor if you have an external MAP sensor. Everything else can be plugged to eliminate issues.

- Does the tach move when you crank the engine? Is the tach hooked to the EFI computer or an MSD box? If you are getting a tach signal, then you are
probably getting spark.

- You need to figure out why the fuel psi is not staying at 42 when the pump shuts off. Mine will go down to maybe 40 when the pump shuts off but that is it. If you extend the prime time in the software, the pump will still be “priming” when you start the engine. Then, once the engine gets past the “Crank to Run RPM”, the ECU will send a fuel pump signal. The whole reason for that is so the pump is not running when the engine is off in an accident.

- How are your fuel lines plumbed? Can you isolate your fuel line from the injectors and plug the line? I use AN fittings so mine is easy to plug. You can then isolate the issue.

 

The Fast ECM must see voltage at both "key on" and "start". If it isn't wired correctly (at the ignition switch) then the ECM will not be powered up while cranking. Many builders overlook this fact.

Are you using a mechanical fuel pressure gauge or a transducer in the fuel line receiving a 5volt signal from the FAST ECM? If you are using a transducer that is getting a 5volt signal from the FAST ECM ........ the gauge might be instantly dropping to zero (during cranking) because your ECM is not staying powered up during cranking phase.

With the ECM not being powered up during cranking.......it will never see pulses from the crank/cam sensor so it will never re energize the fuel pump circuit.

 

The front vacuum line is usually referred to as a "ported" vacuum. It is usually hooked up to the vacuum advance canister on the distributor (if equipped). I would plug that line unless you upgraded to a HEI type distributor.. On the back, the two larger vacuum lines would most likely be "manifold" vacuum. One line should be dedicated to the fuel pressure regulator and the other line should be shared by the HVAC controls, headlight/wiper door systems and the brake booster if installed. Your Fast install manual should describe this in more detail. The MAP sensor may require its own dedicated "manifold" vacuum source as well. This vacuum line should be as short as possible. These features should be pointed out in the install manual.

 

Aloha All,

I found the following from a Edelbrock specialist who work with the FAST collaboration team, (they merged in 2020 under The Edelbrock Group, which includes Edelbrock, FAST, COMP Cams and others)

"When you first Key On, the fuel pump should kick on for a few seconds. Make sure you are seeing the fuel pressure gauge kick up to over 30psi. When the pump stops the pressure will bleed down pretty quickly. This is normal because there is not a check valve in the fuel system.
If all that checks good, then next watch RPM and Battery Volts On The Touchscreen while Cranking.
RPM should be 100-200 while cranking. Batt Volts should not drop below 10v while cranking.
If you are missing either of those the engine will not start.
Matt Maxwell
Calibration Specialist
Edelbrock Group"

I will double check all the plumbing and report back, just to be sure.

Thanks Ken & Steve for the Vacuum breakdown.
I hooked it up due to something I read in the installation instructions, but re-reading it that may just be for a dual plane application.

I have the Dakota Digital RPM display hooked up via a Ron Francis controller, so the gauges drop power during cranking, so have to use the FAST controller to see the RPMs from the ECU live data.
I did check, they are hooked up to the correct port on the Ron Francis.

The RPM module I may have wired that incorrectly. I am using a MSD 6AL and wired the RPM module into coil. this may be causing a conflict. its not as the RPM module is not needed is not needed with my set-up,

I found the following.to help.
There are two basic options for supplying the EZ-EFI™ ECU with an RPM input.
An aftermarket capacitive discharge (CD) ignition box which is recommended or the supplied RPM Module.
"To connect an MSD 6AL to a FAST EFI system for RPM input, you must use the gray tach output wire from the MSD box and connect it directly to the designated tach input on the FAST EFI harness"

Hopefully this will fix my issue.
​​​​​​I am thankful for all the inputs, Hopefully all this information could help someone in the future.
Stay tuned, I probably will be able to check the plumbing on Sat/Sun and get to the wiring on Monday, (Weekends, I work 12hr night shifts)

 

I find that very interesting. I've worked on a number of EFI systems. I've never heard of a system without a check valve.
Kinda like what's the point of the pump running in the first place if the fuel pressure dies before you can start it.
No fuel, won't start.

 

Aloha all,
@4-Vettes, I think it is strange as well that the pump primes but doesn't hold pressure for the starting sequence, yet that is what the Edelbrock/FAST specialist stated.

I followed the fuel lines this morning there is the stainless steel braided PTFE line that runs from the pump output to the front of the EFI carburetor.
Then from the back of the carb to the fuel regulator, returning on a braided Nylon PTFE hose. Yes, I understand that some people prefer stainless lines vs the rubber/Nylon PTFE, maybe this is a future upgrade. For now I just want the car to start. I also took apart the fuel regulator to make sure it was clear, clean, and plumbed correctly, the only thing I noticed is the it didn't have a ball bearing under the regulator screw like the last one I took apart on my 1990 C4, could be a different design. So I think were good on the fuel direction and regulator.

I didn't have time to dive into the wiring yet, maybe I can start cutting the tape in the morning and rewiring on Monday. I also just found out my wife's passenger HID headlight went out, so I have to take the bumper off her SUV to change that on Monday. (Yeah look up 2011 Lincoln MKX Passenger side HID headlight, you really have to take the whole front bumper off the vehicle to get to the ballast, its a real PIA)

With any luck I have the C3 started this upcoming week and hopefully put back together where it can be driven next spring.
Thank you all for you input on this journey.
V/r,
Karp

 

I read all of that twice.
Where is this pump located? Why on earth doesn't it have a check valve.
It should be in your fuel tank. I have seen leaks inside the tank between the pump and the bulk head connector. Did you check?
If you have a inline pump, change it.

 

Aloha 4-Vettes,
Good point I should have posted that in my first post. I have an external pump feed from a custom stainless 25 gallon tank (no spare tire). Ordered a new 300LPH pump and matching fuel regulator, it should be here in a few days. Never hurts having the spare parts on hand. Thinking of installing a shut off valve after the tank and before the in-line pump & filter, it would make it easier to change the filter/pump. My tank is gravity feed out the rear bottom

Will re-wire work on rewiring the RPM module Monday/Tuesday. Then if all goes well, it will start and I can move on to the next part of this project. Thanks to all.

V/r,
Karp

 

Aloha All,

I decided to change the fuel regular first as the glass on the guage was cracked, and I was rewiring the tach signal to the efi then move onto the new pump.

The fuel regulator guage decided it was going to come as I was taking it off.

The system is now holding pressure and better yet the Vette started for the first time in two years!

Many thanks for everyones support.
now to get it in turned and stay running, lol.
V/r,
Karp