Starving for fuel

[GB SISSON]

I have been using the search thread on this, but not finding what I want. My 47 tonner starves for fuel on hills. I have an inline electric 'primer' pump and depressing it's momentary switch brings the engine back to full power cresting the hill with ease. I use the same pump on two other flatheads with great success, so I know they flow through. Tank is red-coated, all new lines and clean clear filter. Gravity flow through filter is a solid stream. Fuel pump pressure is 3.4 psi at cranking and it fills a jelly jar/juice glass to 3/4" depth in ten seconds at cranking. Are these numbers good? Also I have tried two different rebuilt carbs with no change. Can it be the stock pump or push rod with these numbers? Thanks very much in advance.

[rockfla]

Our 32 experienced this exact issue when we had it in the mountains of CA.....we are in FL......it ended up being the float level in the carb.

[GB SISSON]

I don't think that's what is wrong with mine. I rebuilt the carb that is now on it and I set the float level at that time. I guess the push rod has shortened over time? Tomorrow is Saturday so I might just pull the pump and swap it and measure the push rod. I have 4 or 5 of them around or weld the top. This truck was originally sold to a resort in the mountains of Northern California. Rimrock Ranch in Old Station Ca. It came with the original pink slip and the key fits the door and the ignition.

[Tinker]

GB i'm sure you know but check the oil/pump stand to make sure it's not bent. If the wrong order of gasket and baffle installation from a previous owner, it can result in bent ears. You can always try a playing card as a pump gasket to add a "very" little extra pressue.


A tack weld can't hurt.


If I read right you run both mech and a electric pusher. Pusher should be a bypass unit.


3-4 psi sounds very good though. More then enough


same under heavy load? vacuum under load too?


Maybe a bad powervalve if its a 94 and the vacuum looks good.

[Ken/Alabama]

Could be your pump is sucking air around the lid if it's a steel bowl type pump or around the glass bowl if it's that type.

[Mart]

Sponsored Links (Register now to hide all advertisements)

If you decide you want to lengthen the pushrod, the ones I have had are a tubular centre part with two hardened ends pressed in. they have a spline to make them a good fit. I have pulled the end out, put washers over the part that presses in and refitted the end. After fitment you have to lick the OD of the washers down with a grinder.

Done it a couple of times, it works.

Mart.

[GB SISSON]

Good ideas! I'll head down to the shop and see what I find. Is there a standard test for flow from the pump such as so many ounces in a certain amount of time? Thanks!

[RobR'35]

The spec. for the "travel" of the rod is .200" that of course is based on the lobe ground on the cam.
Of the two rod lengths I'm aware of one is 7.872 the other is 8.872.

[GB SISSON]

I pulled the fuel pump and stand. The base was bent out by 1/16" so I ground it flat on my stationary disc sander. I also found a suction side line without a hose clamp so I added one. Then I swapped out the fuel pump for one I bought last year to keep as a spare. I think it was from a 41 merc and was rebuilt for ethanol gas. I miss the glass bowl though. The rod was exactly at 7 7/8" so I didn't touch it. Pretty loose in the bushing though....Took a test drive on all the hills that it failed on before. Very good power and throttle response. I would call it solved! On return I decided to do a compression test. This engine has been sitting a long time and no history other than the man from Oregon that sold me the truck said he got the engine from a friend who had it in a 36 coupe and wanted the correct year engine. It smoked badly at first but has gotten way better after changing oil and running it pretty hard. Today's compression was 75,82,82,85,92,92,90,92. The 75 went to exactly 92 with some oil, so I'm hoping stuck ring in there. Idles at 18 vacuum, very steady. After a run it idles at 10 lbs oil pressure, but the gauge is screwed into the block so I don't know going down the road. One thing for sure, now that I can roar down the winding roads I need to address the 6 1/2" (after adjustment) play in the steering wheel. I have a rusty tonner parts truck that has 2 1/4" play and I haven't adjusted it. I'm sure I will post about that swap, but I thank you all for helping with today's successful outcome!

[40cpe]

Originally Posted by RobR'35

The spec. for the "travel" of the rod is .200" that of course is based on the lobe ground on the cam.
Of the two rod lengths I'm aware of one is 7.872 the other is 8.872.

Just to add to the above, I went out and measured a rod that I took out of an 8CM engine with a Ford two barrel manifold. It measures 10" to the low part of the worn end that rides on the cam.

[GB SISSON]

Ok... Now it's time for true confessions. After my last post I headed into town (12 miles each way) in the red truck to do some weekend chores. About a mile out she started sputtering again and some pretty loud backfires on the hills. What the heck???? I turned around and thought about what could be stopping the flow. The only thing I had not been through and replaced or checked was the 13.00 electric fuel pump that I had inline. After limping home I pulled the pump with it's provided filter and blew threw it in the direction of flow. Maybe a very slight passage of air, but basically blocked. I still had one of the four I bought on amazon in it's box so I compared that one. It acted like a check valve. Free flow in the direction of flow. No resistance at all in direction of flow, but check valve in opposite direction. Here's what I think. Cheap chinese rubber in gasket/diaphram swollen up and restricts flow through the pump now. It is not debris, as there is a new filter before the pump. I pulled the pump, ran on my new stock type 'mechanical' pump and did the 24 mile round trip with ease. I even went over Kimple Pass and Flarehty's Hill wide open with no issues, (well except for the blowby coming into the cab through the open pedal and tranny holes). Moral of this story is..... A free flowing electric pump out of the box doesn't insure that it will remain so.

[RobR'35]

That red pickup is a tough looking truck. Awesome.

[GB SISSON]

Originally Posted by RobR'35

That red pickup is a tough looking truck. Awesome.

Thanks, it's a true 'tonner'. 122" wheelbase, 8' bed, 7.50 x 17s and a lot of leaf springs. I have some good blocks and a std merc crank so I gotta get it turned and build a good engine for it over the winter. I found the seventh .040 over merc piston so now I just need one more.