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1973 C10 "The Purple Truck"

Basic build
Overview Gallery Discussion
Interesting, we knew it this point it was wiring, but was it ground, power, or interference. If this holds true you have found a power fluctuation that was causing it, nice work!

Also, interesting note for anyone else with the PF4, putting a relay in for the fuel pump is the better option regardless of fuel pump.

Its also funny how they show a 15A fuse in the relay option not knowing what fuel pump or wiring you are using.
 
Once I know for certain the problem is solved, I plan to make a post about it in the PF4 thread and on the Edelbrock forums. It surprises me the tech people never asked about it. So I figure it could be good info for others. It's hard for me to believe I'm the only one that's had this issue.

@folkenheath do you think they will still check out my original ECU/TB? I wasn't sure if by you getting me a new one if they'd taken mine out of the testing queue.
 
Being a mostly oem guy I can’t imagine running an electric fuel pump without a relay. I don’t care if it only pulls 10 amps or less. Electric motors generate “noise” or emi. Having it powered by a computer directly is not a good idea. I’m really surprised Edelbrock even suggested to run that way even on the low amp draw.


Glad you nailed down the issue.
 
ZooMad75 said:
Being a mostly oem guy I can’t imagine running an electric fuel pump without a relay. I don’t care if it only pulls 10 amps or less. Electric motors generate “noise” or emi. Having it powered by a computer directly is not a good idea. I’m really surprised Edelbrock even suggested to run that way even on the low amp draw.


Glad you nailed down the issue.
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That's why I hadn't worried about it too much. Figured it wouldn't be given as an option if it was a concern.

If this does end up being a permanent fix, I will have to clean up the relay install. I just kinda passably threw it together to test a theory not holding out much hope it would make a difference.
 
I also thought it was strange they have a fuel pump direct wire option in the instructions. I just went through this wiring my PF4 and I decided to use a relay, ordered a genuine Bosch. Hope it fixes your setup. I still think its weird that the TPS circuit was affected.
 
mrk5 said:
Once I know for certain the problem is solved, I plan to make a post about it in the PF4 thread and on the Edelbrock forums. It surprises me the tech people never asked about it. So I figure it could be good info for others. It's hard for me to believe I'm the only one that's had this issue.

@folkenheath do you think they will still check out my original ECU/TB? I wasn't sure if by you getting me a new one if they'd taken mine out of the testing queue.
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It's probably not very common because most likely most did put a relay in regardless.
I would have.
 
Interesting to see if this fixes it. I wouldn't have guessed it, since I don't have enough experience in these areas.

I used a relay so that I wouldn't have to worry about a bad wire or pump killing the fuse for the ECM. Separate fuse should help me, was my thinking. As since GM used a relay on TBI, it made sense to me.
 
Hoping Neil Patrick Harris GIF
 
Bent77 said:
What is your charging voltage and amps?
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I will have to look see what it is now; I don't recall looking at it.

I installed a high amp alternator back in the summer because I noticed with the AC running the voltage was dropping below 12.5 at idle. At that time I thought maybe that was going to solve my TPS issue thinking maybe it was a voltage drop problem.

Looking back at the last screen capture videos I recorded before sending stuff to Edelbrock, voltage according to the ECU was around 13.5V.

I suspect 90% of people install a relay. I figured at the time I had to buy a pump so why not get a pump that would eliminate the need to add a relay. One less thing to worry about failing.
 
I'm getting excited the truck is still running correctly but I'm almost afraid to get my hopes up.

Another improvement is in starting. Pretty much from the day I first installed the PF4 I've fought with either getting the truck to start cold or not die when I shift into gear. So far that has not been an issue yet. FWIW, I haven't touched any of the parameters; the only thing I set was the throttle speed screw to put the IAC at 5% for the default 750RPM target idle. All of the software settings are same as they came out of the box. Curious to see how the MPG looks.
 
Yep. Starts just fine in the morning and no issue shifting into gear. I feel like I might finally be getting the true Bro-Flo experience.
 
Will you please sort @6872xtc out? He’s having an out of Bro experience
mrk5 said:
Yep. Starts just fine in the morning and no issue shifting into gear. I feel like I might finally be getting the true Bro-Flo experience.
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82355 said:
Daily driver now?

Martin
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Every day this week. I'm back to seeking excuses to drive somewhere because I enjoy the drive again. Kid needs picked up from practice? I'm on it! Service guy needs some lamps? I'm there!


Bent77 said:
Will you please sort @6872xtc out? He’s having an out of Bro experience
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Fuel pump relay cures all.


Now I'm on the engine swap. First I was thinking I would hold off a couple of weeks so I could buy headers, but now I'm thinking about just swapping the engine and do the headers later.
 
mrk5 said:
Every day this week. I'm back to seeking excuses to drive somewhere because I enjoy the drive again. Kid needs picked up from practice? I'm on it! Service guy needs some lamps? I'm there!



Fuel pump relay cures all.


Now I'm on the engine swap. First I was thinking I would hold off a couple of weeks so I could buy headers, but now I'm thinking about just swapping the engine and do the headers later.
Click to expand...
MAW.
 
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