Fuel starvation issue?

[crash89]

I recently woke up my RR after its winters nap. Before I parked it, I put Sta-Bil in the tank and filled it up. I did do some work on it this winter, but nothing to do with ignition or fuel. It ran really well before I parked it.
Fast forward to a few weeks ago. It took a bit of cranking to get it to fire up the first time. That’s to be expected after sitting for a few months. Once running, it ran fine. I ran it several times over the next few days. One pump, a click of the key and she started right up. Then, I backed it out to the driveway. It stalled. Odd. It hadn’t done that while running up to operating temperature and checking for leaks. Which I did a couple of times. Never a problem. So I check the sight glass on the fuel filter. Bone dry. I pushed it back in to the garage. Bowls are dry in the carb. I figure, okay fuel pump died. So I change the fuel pump. It was of unknown age so I figure it may have been time.
I changed the pump and got her running again. Seemed fixed. So I take it for a short drive for about five minutes. Pulled into the driveway and it stalled again. Fuel starved again. Figuring I may have had a blockage in the line, I disconnected the fuel pump end and ran some low pressure air through to see if that cleared it. It seemed to do the trick. I did get bubbles in the tank. So it wasn’t blocked. I ran it a few times over the last several days in the garage and all seemed well. I took it for a longer drive today. Thankfully not too far because I had to send my son home to get my truck and tow it home. While on the drive, it did sputter when the RPM got over 3500 at about 75% throttle.
I know this is long winded, but wanted to give some background before asking my question...
Anyone had this problem before? If so, where should I look next?

 

[wagonman]

Hope you changed the filter? If OK then I would pull the pump and the push rod to inspect. I recently had the same symptom and the rod was worn at the cam contact area. Seems to be a rash of FP rods lately.

 

[Don Frelier]

It could be the pickup screen is getting fouled. If the first couple suggestions don't cure it. You should drop the tank and pull the sender out. I had an 85 with a rusted top and the sound deadening fiber mat had got into the tank. The longer you drove it the mimofibers would build on the pickup.

 

[crash89]

Hope you changed the filter? If OK then I would pull the pump and the push rod to inspect. I recently had the same symptom and the rod was worn at the cam contact area. Seems to be a rash of FP rods lately.

Thanks for the quick reply! I did change the filter. When I changed the pump, I did not inspect the rod end. Didn’t think to check. I didn’t want to pop it out because it can be a PITA to put back in. I’ll likely do that next. I really don’t want to have to drop the tank.

 

[Kern Dog]

The rubber fuel lines may have cracked, even slightly. When this happens, the fuel pump will suck air rather than fuel. Pressurizing the line sort of masks the fact that there is an air leak. Pressure from an air hose may push fuel even if there are several small leaks but SUCTION from a mechanical pump is different.
I've had this very thing happen a few times. Hose clamps can loosen or lose tension. Leaks can develop. Fuel pump pushrods can wear down to where the arm/lever on the pump barely moves.

 

[crash89]

It could be the pickup screen is getting fouled. If the first couple suggestions don't cure it. You should drop the tank and pull the sender out. I had an 85 with a rusted top and the sound deadening fiber mat had got into the tank. The longer you drove it the mimofibers would build on the pickup.

I was really hoping not to hear that. The tank is about two years old. Though it does seem to fit, as well. After letting it sit for a bit, it seems to get sufficient fuel in the line to run again.

 

[Don Frelier]

If the tank is two years old then you should not have the problem I described?
Is it vented okay? Try just setting the gas cap on. Rubber lines good?

 

[crash89]

The rubber fuel lines may have cracked, even slightly. When this happens, the fuel pump will suck air rather than fuel. Pressurizing the line sort of masks the fact that there is an air leak. Pressure from an air hose may push fuel even if there are several small leaks but SUCTION from a mechanical pump is different.
I've had this very thing happen a few times. Hose clamps can loosen or lose tension. Leaks can develop. Fuel pump pushrods can wear down to where the arm/lever on the pump barely moves.

Sucking air in is something I haven’t seen. Looks like I’ll be inspecting all the way front to rear.

 

[crash89]

If the tank is two years old then you should not have the problem I described?
Is it vented okay? Try just setting the gas cap on. Rubber lines good?

Rubber lines are good. But based on what Kern Dig said earlier, I’ll be inspecting that. When I am under there, I’ll see what I can figure out on the vent.

 

[69a100]

You didn't say but, If all the others are fine then start looking at the pump push rod being worn. Good Luck

 

[coloradodave]

Rubber lines are good. But based on what Kern Dig said earlier, I’ll be inspecting that. When I am under there, I’ll see what I can figure out on the vent.

Not a bad idea to replace the short rubber hose off the sending unit, as well as any other hose in the system with "fuel injection" hose. NAPA carries it and it is better equipped to handle today's fuels. Good luck finding the problem. BTW, sucking air through old hoses is a common problem and hard to diagnose, since the hose doesn't leak fuel...

 

[crash89]

Not a bad idea to replace the short rubber hose off the sending unit, as well as any other hose in the system with "fuel injection" hose. NAPA carries it and it is better equipped to handle today's fuels. Good luck finding the problem. BTW, sucking air through old hoses is a common problem and hard to diagnose, since the hose doesn't leak fuel...

Yep. I’ll be looking at that. The lines are only a couple of years old. But I have plenty of spare FI hose. Easy to do. I’m pulling the fuel pump back out today. I was looking and a lot seem to have an issue with the rod. I am really starting to think the rod makes sense. It really seems to starve out when under load.

 

[crash89]

All, many thanks for the ideas. I will post up the fix when I finish. This is a great forum. Not too many old-school guys around me that I know of to bounce these things off of. For this reason, I decided it was time to finally get the gold badge.

 

[wagonman]

Yeah I chased my tail on this same issue. Have a gauge at the carb that read 6psi then after warmed up with a good WOT run up the hill I popped the hood and had 0. It dont make sense but it is what it is. Just hope the cams not FUBAR, put a Comp hardened rod in and will pull it after a few miles to check. Fingers crossed. Put one of the Carter street/strip pumps in as well.

 

[crash89]

Yeah I chased my tail on this same issue. Have a gauge at the carb that read 6psi then after warmed up with a good WOT run up the hill I popped the hood and had 0. It dont make sense but it is what it is. Just hope the cams not FUBAR, put a Comp hardened rod in and will pull it after a few miles to check. Fingers crossed. Put one of the Carter street/strip pumps in as well.

That’s what stumped me.. I had 6psi at the carb when cold. Zero and starved out while coming up the hill to my house. All the checks I have done have shown normal when on level ground at no load.

 

[wagonman]

Exactly the same. My $$ is on the short rod.

 

[Kern Dog]

Exactly the same. My $$ is on the short rod.

Sure you meant to publish that on an open forum??

 

[wagonman]

HMMM maybe the Blue forum?

 

[69a100]

Hey, I went for a drive, car ran fine. Parked it for 5 minutes and I could get mine running no matter what. Found out my push rod was 3/8" shorter then a new one. What do you want after 110K miles? Good Luck

 

[Wietse]

Mine stalled when at WOT....
Later on did nothing at all.