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454 problems after new fuel pump and rebuilt carb

T

turbosonly

New member
"Prior to the the abovemention

"Prior to the the abovementioned changes, the engine started and ran fine UNTIL the secondaries were opened (under load). Then, it would bog down and RPMs would fluctuate.

Since the boat had been sitting with very little use for a couple years (before i got it), I decided to get the QuadraJet rebuilt. The engine shop who took the carb in for the rebuild asked about the fuel pump as well. I showed them pictures and they recommended a HP Elec Marine Fuel Pump by Carter.

I put the rebuilt carb and new fuel pump on the engine using the existing electrical connections. I ran the pump for a while prior to hooking it up to the carb to make sure clean gas was coming through. After that, i hooked everything up and cranked it. Once started, i noticed a waver in the RPM at idle. It would go up and down 150-200 rpm rhythmically. I also noticed the smell of raw gas at the exhaust. Under load it would stall out. The engine also seemed to run rough.

Now, with 20/20 hindsight, i know i should have done one thing at a time, EITHER the new fuel pump OR rebuilt carb.

Any input would be greatly appreciated."
 
what are the specs on that car

what are the specs on that carter pump?

A WAG would be the rebuild wasn't done very well and the pump provides too much fuel pressure.
 
"'Fraid so. The carb need

"'Fraid so. The carb needs a rebuild. And while you're at it, stop depending on that tiny gas filter in the body of the carb. Install a nice, big, all METAL can filter just before the carb to supplement it.

Jeff"
 
It is a P4389 - Carter Univers

It is a P4389 - Carter Universal & Marine Electric Fuel Pump. Has max. pressure of 6psi and 72gph free flow rate. There is a big marine (metal/paper) fuel filter in front of the fuel pump.

I would be surprised the carb was a bad rebuild as the engine shop sent it out to a reputable carb rebuilder they have used for years. I guess anything is possible.

Any other ideas though?
 
Could have just been miscommun

Could have just been miscommunication or marginal parts. 6 PSI will test the fuel inlet systemm to the max. Did they check the needle and seat for positive sealing. Ask what the needle sealing material is. Did they replace the float? Did you check the pressure provided by the new pump?

What RPM does the engine idle at once warmed up?

Does the main nozzle drip at this rpm?
 
You also have the opportunity

You also have the opportunity to run the pump with the engine off. Check the carb carefully for internal drips.
 
"Are you sure you had a proble

"Are you sure you had a problem with the carb to start with? Knowing the history, did you go through the fuel system (filters and lines) and ignition system prior to diagnosing it as a carb problem? What is the quality of the fuel?"
 
I don't know the specifics

I don't know the specifics on the carb rebuild. I haven't checked the fuel pump pressure since i assumed it would be at spec since it is new.

Fuel tanks were replaced as well as the filter. It has good gas now and newer fuel lines.

I didn't suspect the ignition system since the boat ran really well until pushed to WOT.
 
"If the carb is cruded up, the

"If the carb is cruded up, the secondary jets could be partially blocked, resulting in a lean out when you mash it.

Jeff"
 
"Is this a single or twin engi

"Is this a single or twin engine boat? If twin, and you are convinced it is a fuel delivery issue, and the other engine runs good, install the "known good" carb on this engine and see what happens.

I don't know what distributor you have but never assume it is OK because it runs good at lower RPMs. Put your timing light on one of the plug wires then run it up until it stumbles. It your light becomes intermittent and flickery, you should look at the ignition system more closely. Something as simple as a bad plug wire can work fine at lower loads, but fail at higher loads.

I'm not trying to make you chase your tail but a few minutes of troubleshooting can eliminate many other possibilities and allow you to focus on the real cause of the problem.

Good luck
Rick"
 
"You also need to know how to

"You also need to know how to inspect the parts that make up the secondary system on teh q-jet. I haven't seen an "OEM service manual" yet that describes the whole procedure with enough detail to call it "correct and complete."

You also didn't say but I'd guess the boat is used. If is quite possible the carb isn't the OEM supplied unit so, it could have had the wrong calibration since you have owned it. The carb shop rebuilding it quite likely used the original RPD specs, based on the model number of the casting.

Also, Rick's recommendations have significant merit....you have NO idea how many 'carb jobs' have been sold to 'fix' other issues."
 
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