440 starving for fuel under load

[davidwhitaker]

Engine starts and runs fine. Cruises at 75MPH no problem. But recently it begins to act like its running out of fuel when I try to accelerate say from 55mph to 65mph or even at lower speeds.

I have a new mechanical fuel pump. (replaced prior to issue)
Replaced all rubber lines from tank to carb (both tanks)
Dropped fuel tank inspected the pick-up tubes (everything OK)
New Fuel filters (all)
Bi passed Electric Tank selector (still having issue)

I put about 75 miles on the new fuel pump with no problems at all. What am I missing?

Next is will put a fuel pressure gauge at carb and watch it while I test it out. Other than that...maybe my carb??

[davidwhitaker]

I forgot to mention....when it first started to happen, I thought I was running out of gas so I switched tanks. It worked great on the aux tank for a few miles then it did it again, I then would switch back and forth as it acted up.

[M & J]

2 questions:
Stock carb and does it do it when the engine is cold or only after its warmed up?

[davidwhitaker]

Its the Edelbrock 1905. I guess this is not the stock carb.
I suppose it only does it after it warms up a little, but it does not have to be super hot. Yesterday it began acting up at around 170deg. or so.

[M & J]

Edelbrock... I would look for an accelerator pump problem. I think Holly's were real bad but mainly when warm sounds like it's lean and not getting the extra fuel shot when wanting to accelerate.

[Rickf1985]

Change to ethanol fuels will call for a change in the fuel rods and maybe a change in the main jets on at least the primary side of the carb. The 1905 is the Edelbrock replacement Quadrajet. It is not the AFB style.

[BrianB]

Rick,


Ethanol has been in fuel for several years now. That alone wouldn't explain a sudden recent change.

[davidwhitaker]

Ill put the pressure test at the carb 1st, if I am still getting good pressure then I will rebuild carb. I am thinking it is the carburetor myself.

[Froggy1936]

Tip:  You can get a good pressure reading but still lack the required volumn . Advise also to pump into a container to check the amt of fuel delivered in 10 sec Should be a quart or more   Frank

[davidwhitaker]

My Dad told me to replace the coil....I did that and it "seems" to be running great now. Go figure! We will see after a few more runs on the highway.

[PwrWgnWalt]

Hi David,


Hope the coil was the issue and you are trouble free...  if not, here's one other thing to consider in addition to everything that's been mentioned:


Have you replaced the fuel caps, or done anything else that might have restricted airflow into the gas tanks?   (creates a vacuum as the first bit of gas is used, until the vacuum is greater than the pull of the fuel pump)

If it acts up again, simply remove the gas cap from the in-use tank to see if that solves the issue.

- Walt

[tiinytina]

Also check your spark plug lines and plugs.. Gone did this same thing... turned out we were running on 6 cylinders not 8 due to 2 wires fried etc...  tune up time....  did the trick. 

[davidwhitaker]

Not the coil. and it runs the same with the fuel cap off.

A mechanic told me to install a HO mech pump or just put in an electric pump. The engine ran fine until I replaced the old fuel pump. He looked up the part number of the pump that Orielly sold me and he said it was NOT a HO Pump. He felt that this application would work better with a HO pump.

[Rickf1985]

You will probably find that pump was an "offshore" manufacture pump and not up to standards. As Frank pointed out you can have good pressure at idle but you need good volume at speed to keep that pressure up.

[legomybago]

Did you put a gauge on it? I would do that before buying parts.  OR... Put the old pump back on! 

[Sasquatch]

I fought this for years on my 440 with an Edelbrock carb.  A couple of things.  Most mechanical pumps you can buy today are junk.  They can not handle the pressure and flow requirements of a thirsty 440 pulling that much load.  I even added an electric lift pump prior to the mechanical, no change.  I then removed the mechanical and ran just the electric pump, still no change.  I was somewhat convinced that the carb was vaporlocking while hot under a load.  I gave up and went to fuel injection.  Runs like a scalded ape now, with more power, better mileage, and much better drivability.

[davidwhitaker]

replaced base gasket on carb...ran like champ for 30 miles...then back at it.

Loosed the gas cap and it ran for 100 miles WITH NO ISSUE AT ALL. And then at the last turn of my trip...starving for fuel again.

SO I can say its getting better. Before I couldn't drive 5 miles without having trouble. So I will install an inline elec pump and see if that solves it.

Sasquatch...what fuel injection sys did you use?

[Rickf1985]

I will bet you find that the cap tightened itself up while driving. Does not take much for that o-ring in the cap to block air going in. get a vented cap. My guess is that your tank vent became the home for a mud dauber or something like it.