Engine ignition or fuel problem

[chargerdon]

On my 74 Challenger with a 360 in it a problem started about a week ago.   While fully warmed up and driving home, I noticed while cruising 50-60 mph a "surge" coming and going.   At first I thought it was the air conditioner compressor kicking on and off as it was a cool day but i had the air on.   

Then the surging stopped and it ran normal.   Thursday evening started her up and after about 3 miles of driving the surging started again, only much worse, to the point that it would surge and then lose power.   By the time I got near my destination (5 miles) the engine lost most of its power and would almost stall.   Pulling out from a stop I had to ease..ease into the throttle or it would bog down.    Very little power.   Shut her off and was at a meeting. 

Two hours later started her and it seemed normal, but, then within first mile it started to surge and then lost power and again had to be gentle on the gas peddle or it would bog down.   Managed to get her home and with engine idling (not all that bad an idle) used my infrared temperature sensor and found three of the cylinders running cool (145-160 degrees).    Shut her off thinking that maybe my plugs had begun to foul.   

Next  morning pulled those three and two more plugs thinking they were fouling...but..they looked good..   Mostly clean.   Started her up and it seemed to be running ok, Good temp about 225-250 on all cylinder headers, took for a spin and withing 1/2 mile the surging started again, then again lost a lot of power...  So problem still there.

I then swapped out the coil with another MSD BLASTER 2 like in the car, and she seemed to have full power back, but, on test drive, same problem came back within a half mile.   Thought maybe it was the ignition coil radio suppressor so disconnected it and same issue. 

So, not sure what to check next...  It seems that when car has a chance to sit for 10 minutes or more the power comes back but then goes away within 1/2 mile or less...and have to limb home. 

Is this fuel problem or ignition???     It has a 600 cfm Edlebrock carb and a high performance mechanical fuel pump.   

I wanted to complete the ignition possiblilites so I took the Ignition Control Module off..   and noticed that it is a 5 pin ECU...   Aftermarket.   I tried swapping it with my 66 Chargers ECU but it is 4 post even tho connector is 5 post, and with it no spark at all on the car...   Looked online and it seems that all of the ECU's advertived all have 4 pins...room for the 5'th but just four pins.   Can anyone explain to me Why mine has 5 pins and a 4 pin apparently wont work???   Help here as even if my problem is fuel, I sure would like to buy a spare ECU.

I checked all the wires, no visible arcing, all vacuum hosed tight.   Not sure what to do next. 

So my questions are...   
1) Electrical ignition issue, or fuel problem?? 
2) What is the 5'th wire to the ECU and is there a way to modify it to not need it, or where can I find a replacement 5 pin ECU ??

THanks

[DocMel]

Start with the basics.  Try fuel filter next

[73440]

http://www.mymopar.com/downloads/Dual_Ballast_5pin.pdf

Here is a 5pin wiring diagram.

[jhaag]

seems car is starving for fuel. replace filter, make sure pump is not dying.

[cudabob496]

fuel pressure too high?

how do distributor cap points look?

float setting?

[cudabob496]

a saying Ive heard: when an engine won't run, 90% of time its electrical problem, and
10% of time its fuel problem.

[dodj]

Start with the basics.  Try fuel filter next

This has my vote!
Change the filter, check in the inlet sintered filter.

[chargerdon]

Thanks guys...after a lot of trial and error...I ended up replacing the mechanical fuel pump with a new one from Carquest, and the problem is gone.   What is strange is that after verifying that the new fuel pump fixed her, I then took the old pump apart and the internal bladder was fully intact and no signs of what might have caused the problem.   Maybe the internal fuel pressure regulator went bad !!   

Thanks again you guys are awesome !!

[jhaag]

Glad it was an easy fix. I was pretty sure it was fuel related. 

[jimynick]

Take a good look at the actuating arm of the old pump. Is it worn? As you may know, they run on an eccentric mounted on the nose of the cam. I've had a pump malfunction internally and pump a few quarts of gas into the oil too, so check your oil level and smell it for a gas smell. If all that checks out, hopefully it was just a bum pump. As mentioned, I'd also consider replacing the $3.00 filter as well- just in case. 

[chargerdon]

Problem came back after about 50 miles of driving....    Took the carb apart and found the fuel bowl on accelerator pump side was dry.   
Took out the float needle and then the seat and the inlet filter was clogged.   Cleaned it and put back together and the problem is now truly solved.    Replaced the fuel filter and hope this never happens again...   

[Strawdawg]

  glad you nailed it!