Fuel pump & carb replacement
#1
My 69 Mach 1 428 CJ needed to be freshened up so I purchased a Holley #12-390-11 fuel pump and a Holley #4160 750 carb to replace the original ones. I installed both along with new 3/8” fuel lines. I tried to start it but it won’t run. I have to keep pumping the gas to get it to start but it will barely run and only get up to about 1000 rpm with my foot to the floor. I tried the original carb with the new pump and same thing. I tried the original pump with the new carb and same thing. Only thing I haven’t tried is putting back all of the original stuff. Timing is good. I get no back fires or explosions. I could find no vacuum leaks. I tried adjusting the idle mix screws both directions and it did not help. Float levels were good the first few times but are high on both now. I checked the pressure at the fuel line split and got just under 10 psi which is too high. The guy from Holley said the pump was bad. I received the replacement today and still am getting the same result. I might not have checked the pressure correctly using a borrowed gauge meant to be used on fuel injection systems. It ran decent before I started. Could the fuel line size be causing problems? HELP  Huh
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#2
After reading your post many times. It would seem you've got the 3 things required for an engine to run. Fuel / Air, Ignition, (at the right time), Compression (engine ran before). So the best I can offer is to go back to the basics. #1 Test the Compression. Your 428 should produce numbers in the 150 psi range. (if it's the original 69 Motor, and hasn't been messed with). #2 Test the fuel flow, Pull the line off at the carb, add a hose to the line, and run it into a quart jar, crank the engine. You should get a large stream, and fill the jar in 5 to 10 seconds, if not quicker. #3 Check the timing,  pull the distributor cap, crank the engine, and make sure the rotor turns, find top dead center #1 and see if the rotor points to the #1 plug wire? It's not common, but the shear pin in the distributor gear can shear, and the timing have moved a few degrees possibly causing the sluggish running as described??? It sounds like you have some knowledge, and skills so going through the basics a little at a time, should find the culprit? Here's Hoping. 

JTS
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#3
The one other thing is a vacuum leak. I know you stated you couldn't find on, but remove the carb and the gasket check all mounting areas and see to it they are mating all the way around the base of the carb and also the intake. I have seen it happen where a gasket doesn't exactly match and you will have an open  area under the carb which would be damn near impossible to find. Another thought is the vacuum booster for the brakes? Let us know what you find, and keep asking questions we'll eventually figure it out.

JTS
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#4
(07-06-2020, 07:37 AM)JTS71 Mach1 Wrote: The one other thing is a vacuum leak. I know you stated you couldn't find on, but remove the carb and the gasket check all mounting areas and see to it they are mating all the way around the base of the carb and also the intake. I have seen it happen where a gasket doesn't exactly match and you will have an open  area under the carb which would be damn near impossible to find. Another thought is the vacuum booster for the brakes? Let us know what you find, and keep asking questions we'll eventually figure it out.

JTS
Thanks for your replies JTS71. I really appreciate it. Concerning your first reply: #1 - I tested the compression last fall and got 190# - 200# on all eight cylinders. #2 - Fuel flow is good. #3 - Timing is good. New MSD distributor and electronic ignition. The rotor is turning. 
Concerning your second reply: I have gone over everything and can’t find any vacuum leaks.
I believe I have figured out the problem since I first posted. I did a pressure test on the second fuel pump with a different tester that gives me a more accurate reading. This test came up at 9.5 psi. Way too high. Should be at 6.5 to 7 for this carb per Holley. So another bad pump. I’m calling Holley today to complain and ordering a different brand pump from someone else.
Thanks.
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#5
Well I'm not sure that 9.5 would cause the issue. Unless its just absolutely flooding the engine. And if so, you'd be belching tons of black smoke, and fouling plugs??? While I agree 9.5 is to much. I can't believe it's causing this issue? Unless perhaps you left out the belching black smoke part. LOL!

Let us know how it goes. 

JTS
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#6
(07-07-2020, 09:05 AM)JTS71 Mach1 Wrote: Well I'm not sure that 9.5 would cause the issue. Unless its just absolutely flooding the engine. And if so, you'd be belching tons of black smoke, and fouling plugs??? While I agree 9.5 is to much. I can't believe it's causing this issue? Unless perhaps you left out the belching black smoke part. LOL!

Let us know how it goes. 

JTS
The car is in my garage and I would definitely notice any clouds in there but haven’t had any. I haven’t pulled any plugs yet, a real pain in the arse on that engine, but may do so soon just to check. I’m going by what Holley is telling me.
I called Holley yesterday and they researched their call archives. They found one with the same situation on a marine engine. They figured out that the arm was sticking in too far and compressing too far. They added a second gasket and that fixed the problem. I said that might work and hung up. Then I realized that the pump should have shut down at the max psi anyhow so that can’t work. He didn’t think of that either. I’m going to call them again today. I might just go ahead and get a different brand pump or just get a regulator and see if that works. Holley says that 6.5 to 7 psi is ideal for the 750 CFM carb I have. Crazy
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#7
I haven't been here much because I've been consumed with another project.  Yes, fuel pressure is too high.  Holley sadly, doesn't have very good aftermarket mechanical street use performance pumps.  For mechanical pumps, you're better off with a stock replacement, a Carter street performance pump, or an Edelbrock Performer RPM fuel pump.

Now the max 1000 RPM issue. I didn't read all the details, but one thing that comes to mind is check the throttle travel. The stock throttle cable bracket will not work with universal Holley carburetors.  You will need to modify the bracket to get full throttle travel.
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#8
(07-11-2020, 09:02 AM)1969_Mach1 Wrote: I haven't been here much because I've been consumed with another project.  Yes, fuel pressure is too high.  Holley sadly, doesn't have very good aftermarket mechanical street use performance pumps.  For mechanical pumps, you're better off with a stock replacement, a Carter street performance pump, or an Edelbrock Performer RPM fuel pump.

Now the max 1000 RPM issue.  I didn't read all the details, but one thing that comes to mind is check the throttle travel.  The stock throttle cable bracket will not work with universal Holley carburetors.  You will need to modify the bracket to get full throttle travel.
I have been researching other brands. The Edelbrock has a max of 6 psi. Holley says 6.5 to 7 psi is ideal. I looked at the Mr. Gasket but it looks to be an offshoot of the Holley. I haven’t got around to the Carter yet but will today.
The RPM issue is from the carb being flooded. I am aware of the throttle issue and all I need to do is cut off a little bit of the cover on the cable between the ball connection and the bracket. I may try to find a new bracket also.
You would think Holley would know how to make pumps to supply their carbs with the correct pressure but I’ve found out that isn’t the case.
Thanks for your suggestions. Thumbup
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#9
National Parts Depot use to sell a stainless steel throttle cable bracket specifically for use with an aftermarket universal Holley carb.

I use the Edelbrock Performer RPM fuel pump on my 351W with a Holley 700 CFM mechanical secondary carb.  At 6 psi fuel pressure everything works just fine.
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#10
(07-12-2020, 06:28 AM)1969_Mach1 Wrote: National Parts Depot use to sell a stainless steel throttle cable bracket specifically for use with an aftermarket universal Holley carb.

I use the Edelbrock Performer RPM fuel pump on my 351W with a Holley 700 CFM mechanical secondary carb.  At 6 psi fuel pressure everything works just fine.
I decided to go ahead and order the Edelbrock. It shouldn’t have any problems with the 750 on my 428 CJ. I’ll check NPD for the cable bracket. I like using them. They had a lot of the stuff I needed for my 68 Cougar and now my Mach.
Thanks for the info.
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