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1966 GT Fastback, 289 EFI, T5z
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Discussion Starter · #1 ·
I'm not sure if it's the worst or the best thing that could happen at a car show. At the conclusion of a show on Saturday, I started up my '66 Mustang and started heading out. I drove about 200 feet, when the car just quit suddenly and could not be restarted - no power to the fuel pump. Seriously, that's got to be the most embarrassing thing that can happen to you - your precious show-off car craps out in front of all the other super gearhead attendees. Looked at another way, however, this may have turned out to be the luckiest place for this to happen - in less than 30 seconds, a group of 5 or 6 guys came to my aid and pushed the car back into a safe and convenient parking space. This was followed by a whole bunch of discussion about what could be wrong - "what about this, look here, try that" - but to no avail. I locked up the car, and one guy was kind enough to give me a ride (in his beautiful Porsche) back to my house a short distance away. I was able to get a flat bed tow quickly, and the Mustang was safely back in the garage in about 45 minutes,

The first thing I did was check fuses - nothing blown. I then checked the fuel pump - I disconnected the electrical leads to the pump, and it ran fine with alternate battery power. I put a multimeter on the disconnected leads and found that when the ignition key was turned on, 12V would initially appear briefly, but then fade to 0 volts in about 2 seconds. This car has multiport fuel injection (Edelbrock Pro Flo 4) controlled by an ECU which supplies power to the fuel pump via a relay. Some reading / research revealed that this could be an issue with the relay itself. I checked all the connections to the ECU and the relay, then reattached the leads to see what error messages the ECU display could be showing. I turned the ignition key, and lo and behold, it started right up and ran just fine. This is both a good thing and a bad thing ... at least nothing had permanently failed, but what if anything did I fix? ... and when might this happen again?

Questions for VMF'ers - what do you think could cause the fuel pump to cut out like this? It does seem to be tied to the fuel injection, because nothing was actually blown / broken. Why would there be some initial voltage on the fuel pump leads that would fade?
 

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I have the PF4 and removed the FP relay I was using with the FiTech during the install. I can’t remember if the PF4 comes with a external relay in the wiring loom or if it’s in the ECU? If it’s external to the ECU it might be worth buying one and swapping it out.
 

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I don't know anything about the proflo4 but I assume it's supposed to turn on the pump for a few seconds to prime then shut off until the car is started. This is normal on a lot of efi setups
 

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1966 Mustang GT 4spd
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I know the ECU is supposed to have the ability to control the fuel pump up to a certain amperage, however I still installed a separate relay for power to the tank just in case the pump were to go bad and start pulling more than the ECU could handle.

Chris
 

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1966 mustang coupe
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I just ordered a sniper efi and thats what i fear about those units....

My carb never let me down, its never perfect and i sometimes bring my screwdriver with me but i never got stuck on the side of the road...

I will keep my carburetor on the shelf for a while just in case..... :)
 

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67 Fastback T5 331 TCI Frt End, Canted 4 link rear susp
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I just ordered a sniper efi and thats what i fear about those units....

My carb never let me down, its never perfect and i sometimes bring my screwdriver with me but i never got stuck on the side of the road...

I will keep my carburetor on the shelf for a while just in case..... :)
Maybe in your trunk rather than a shelf...LOL
 

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I don't have this Edelbrock EFI, but I looked at it at Summit and the installation PDF. It looks like a complete system except you are on your own for the high pressure fuel pump and vacuum regulated fuel pressure regulator.
First, I would triple check everything electrical on your car that is not Edelbrock or is not fuel pump, i.e. ignition switch and grounds.
Second, the fuel pump system, everyone reading this has no idea what setup you are running, in tank, external, the fuel line configuration, any safety switches such as inertia or roll over cut offs for the pump, ect.
Do you run a low pressure pusher pump to the high pressure pump?
Edelbrock is known to match their systems, so a Edelbrock brand fuel pump and regulator set up as per the instructions would be a good idea.
Third, there are several connected systems and the chance of some kind of failure is greater. The ECU, distributor, the tablet, the phone app, the harness, the sensors, all are prone to fail at sometime, whereas a spare factory EFI component could be had at RockAuto, there are lot of spares to have with this system if it ever becomes unsupported by Edelbrock.
Good luck and let us know what you find.
 

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When I turn the ignition on the pump runs for 5 seconds or so and then shuts off. I'd imagine if the PF4 didn't sense any fuel pressure building it would shut off sooner. I suspect the ignition switch. I have had 2 occasions in the last 10 years on late model stuff of the ignition switch getting iffy resulting in weird behaviors similar to what you describe. And if your ignition switch is new or almost new I would consider it even more suspect sadly. Just my 0.02¢
 

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1966 GT Fastback, 289 EFI, T5z
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Discussion Starter · #11 ·
Sorry about the incomplete system description. Besides the Pro Flo 4 fuel injection setup, I am using a Tanks Inc fuel tank and an in-tank Walbro high pressure fuel pump, with both supply and return fuel lines. The pump is connected to the ECU fuel pump trigger wire through its own relay.

To be more specific, when the problem is present as described above, the ECU does not even trigger the 5-sec fuel pump prime cycle. 12 volts shows up for 1-2 seconds on the pump leads, but then fades away, and the pump itself never makes a sound.

It seems there are others experiencing this issue with relay ground triggers. Here are a couple of screen shots from the Edelbrock Tech Forum that specifically address this problem:

800185


Apparently, carbon deposits or corrosion can form on the contacts of the relay and prevent proper electrical contact. At least two others on the Edelbrock site implemented this solution - replace the main ECU relay - and the problem was solved. I am going to replace both relays in my car, then drive the car somewhere (with a tow truck following me).

1624368225181.png 1624368334008.png 1624368427179.png
 

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Could the low amp and high amp contacts be reversed wired? Relays use a low amp side to control a high amp side.
 

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Nothing to add to your pump issues, but my most embarrassing moment was rolling up to the start line of an autox, pushing in the clutch and having the clutch slave cylinder puke its guts out onto the header collector. Huge smoke cloud rolls up and car goes nowhere. Obligatory Ford content. This was in a Sunbeam tiger so the engine and trans were Ford products.
 

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Discussion Starter · #14 ·
Could the low amp and high amp contacts be reversed wired? Relays use a low amp side to control a high amp side.
Hard to imagine how that would happen in the main relay supplied by Edelbrock. But it is something I should check in the separate pump relay circuit that I installed.
 

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Discussion Starter · #15 ·
Nothing to add to your pump issues, but my most embarrassing moment was rolling up to the start line of an autox, pushing in the clutch and having the clutch slave cylinder puke its guts out onto the header collector. Huge smoke cloud rolls up and car goes nowhere. Obligatory Ford content. This was in a Sunbeam tiger so the engine and trans were Ford products.
Now that is embarrassing ... o_O
 

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Could the low amp and high amp contacts be reversed wired? Relays use a low amp side to control a high amp side.
If so the relay wouldn't ever work.
 

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Sorry about the incomplete system description. Besides the Pro Flo 4 fuel injection setup, I am using a Tanks Inc fuel tank and an in-tank Walbro high pressure fuel pump, with both supply and return fuel lines. The pump is connected to the ECU fuel pump trigger wire through its own relay.

To be more specific, when the problem is present as described above, the ECU does not even trigger the 5-sec fuel pump prime cycle. 12 volts shows up for 1-2 seconds on the pump leads, but then fades away, and the pump itself never makes a sound.

It seems there are others experiencing this issue with relay ground triggers. Here are a couple of screen shots from the Edelbrock Tech Forum that specifically address this problem:

View attachment 800185

Apparently, carbon deposits or corrosion can form on the contacts of the relay and prevent proper electrical contact. At least two others on the Edelbrock site implemented this solution - replace the main ECU relay - and the problem was solved. I am going to replace both relays in my car, then drive the car somewhere (with a tow truck following me).

View attachment 800186 View attachment 800188 View attachment 800189
That could definitely be an issue. In the avionics world, we use the term " got Fluked" because sometimes when using a digital ohmmeter, you can use a Fluke meter and see 28 V on a circuit, but the end user ( light, motor, etc) will not operate. Many times, I use a load light to confirm power to a system. I have found that on stranded wire, if you have one strand left, or the wire is broken and just touching, the Fluke will show good power, even thought the conductor cannot pass the amperage to allow the component to operate.
With burned contacts, the resistance added will drop the voltage under load, where you may not see any indication when just reading it with a meter.
A friend of mine had a Bobcat that had starting issues. We found that in the 24" of 2/0 battery cable, the voltage dropped from 12 VDC to around 5 VDC at the starter. I cut off about 3" of the cable and fixed the problem. Electricity can be interesting. Always verify your assumptions.
Good luck. I am planning on getting the PF-4 system myself when I get to that point, but will probably opt for a more robust relay for the fuel pump.
 

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Discussion Starter · #18 ·
That could definitely be an issue. In the avionics world, we use the term " got Fluked" because sometimes when using a digital ohmmeter, you can use a Fluke meter and see 28 V on a circuit, but the end user ( light, motor, etc) will not operate. Many times, I use a load light to confirm power to a system. I have found that on stranded wire, if you have one strand left, or the wire is broken and just touching, the Fluke will show good power, even thought the conductor cannot pass the amperage to allow the component to operate.
With burned contacts, the resistance added will drop the voltage under load, where you may not see any indication when just reading it with a meter.
A friend of mine had a Bobcat that had starting issues. We found that in the 24" of 2/0 battery cable, the voltage dropped from 12 VDC to around 5 VDC at the starter. I cut off about 3" of the cable and fixed the problem. Electricity can be interesting. Always verify your assumptions.
Good luck. I am planning on getting the PF-4 system myself when I get to that point, but will probably opt for a more robust relay for the fuel pump.
Thank you for the reply ... this is helpful. Do you have any recommendation for a more robust 30 amp relay, i.e., any that you feel would hold up better?
 

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Yes, let me do some research. I am planning on having the Edelbrock ECU controlling the relay. If need be, we can find one larger than 30 amp, because that is only the spec for the load carrying ability of the wiring/contacts inside. I will give you an idea on what I plan to use, and you can go from there. I am betting cost was a major factor in Edelbrocks relay selection process.
 

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Thank you for the reply ... this is helpful. Do you have any recommendation for a more robust 30 amp relay, i.e., any that you feel would hold up better?
https://www.mouser.com/datasheet/2/418/3/NG_CS_Automotive_Relay_Applications_0315-1650651.pdf is the spec sheet and an interesting read on relays and I think I would opt for this: https://www.mouser.com/ProductDetail/TE-Connectivity-AMP/0-332-019-103?qs=UXgszm6BlbHtCizalJLPFA==. TE/AMP makes good stuff and its rated at 50A and at $13, is pretty cheap. May want to order 2 and keep one in the glove box, just in case.

Hope this helps.

Chris.
 
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