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A fuel problem, Maybe, maybe not

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Coastalman

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Guys, I really need some help on this. It may be something simple, but I have exhausted my limited knowledge. What is happening is this: I can start off just fine, but by the time I am in 5th gear (Datsun 5 speed) and running at 60 mph I seem to be running out of gas. The engine is sputtering and losing power after about a mile. I can then put the car in neutral and coast for a count of four, put the car back in gear and run great for about another mile and then it starts over again. I drove 20 miles like this last weekend and it sure takes away from the motoring experience. Here are the details of what I am working with. I have boiled out the fuel tank twice and the gas coming out is clean. I have now put in the third Facet fuel pump. It is putting out 4 to 4 1/2 pounds of pressure at the carbs with new high quality fuel hose. I have good fuel filters before the pump and again before the carbs. The 1275 engine and carbs were rebuilt less than 400 miles ago. The motor has high compression pistons and a mild cam. I am using a Pertronics ignition and an alternator. I have double checked the floats and needle valves to make sure they are working correctly. Today I changed the fuel cap to make sure it was venting. It seems like the float bowls are not filling correctly at high speed. When I coast, I feel like they are then filling up again and I have fuel until the bowls run low/dry. This has been going on since the rebuild.
Could this be anything else than fuel starvation? I have hit a wall and need help.
Thanks,
Charlie
 
Don't rule out electrical. Check you coil and plug wires for shorts cap and rotor. I just had a similar problem that was very intermittent.
 
Check your hard line between the tank and the carbs and see if maybe theres a bend flat spot in the line.Also could be the strainer screen in the tank is clogged? I would also check the delivery rate of fuel to the carbs somebody here should know how much is needed GPM to keep here happy. With it recovering in 10 seconds or less I dont think it would be the coil. Teflon tape caught in a fitting?
 
Coastalman said:
Guys, I really need some help on this. It may be something simple, but I have exhausted my limited knowledge. What is happening is this: I can start off just fine, but by the time I am in 5th gear (Datsun 5 speed) and running at 60 mph I seem to be running out of gas. The engine is sputtering and losing power after about a mile. I can then put the car in neutral and coast for a count of four, put the car back in gear and run great for about another mile and then it starts over again. I drove 20 miles like this last weekend and it sure takes away from the motoring experience. Here are the details of what I am working with. I have boiled out the fuel tank twice and the gas coming out is clean. I have now put in the third Facet fuel pump. It is putting out 4 to 4 1/2 pounds of pressure at the carbs with new high quality fuel hose. I have good fuel filters before the pump and again before the carbs. The 1275 engine and carbs were rebuilt less than 400 miles ago. The motor has high compression pistons and a mild cam. I am using a Pertronics ignition and an alternator. I have double checked the floats and needle valves to make sure they are working correctly. Today I changed the fuel cap to make sure it was venting. It seems like the float bowls are not filling correctly at high speed. When I coast, I feel like they are then filling up again and I have fuel until the bowls run low/dry. This has been going on since the rebuild.
Could this be anything else than fuel starvation? I have hit a wall and need help.
Thanks,
Charlie
Click to expand...
Maybe a silly question but make sure the points haven't closed up. Pop the cap and turn the engine till the distributor cam is on a lobe and check the gap. This happened to me on the road last fall. It would start and run fine and then jerk like crazy and I thought I had a fuel problem.
 
I forgot to mention that the ignition was checked out on a Snap-On engine analyzer and was showing 100%. All plugs firing correctly and the plugs are a light brown except for #3 which is a little darker, but not wet. I will get under the car tomorrow and check for a pinched fuel hard line. I did break the screen on the fuel pickup in the tank because it appeared to be clogged. I peeled be screen away from the tube in two places. Could that screen be collapsing into the fuel pickup opening? It seemed to be very stiff.
 
I would check and see what volume of fuel you are getting at your last carb in the line.
 
I would run it in a liter drink bottle for the Volume. Time it then measure the results. At least a place to start I figure.
 
Static fuel pressure means nothing if it cant deliver enough gpm when its filling the bowls.
What is the fuel pressure when the bowls are filling? If you have good fuel pressure when at idle - Ignition off power on. Pump is more than likley OK If that is the case but the volume of fuel being delivered is lower than what you consume GPM them it sounds like a restriction of some sort.
 
Facet pump
 

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Based on your description, the problem is almost certainly a fuel flow problem. Remove the line from the carb and let it pump into a container of known size. Record the time it takes to pump a known volume then compare that to the specs. If less then you either have a bad pump or a restriction somewhere.
 
Thanks for those suggestions! I'll pump into a large container and time it. I also had a suggestion to take the fuel tank drain plug out, install a pipe fitting with a barbed hose fitting on it, connect a hose from that directly into the fuel pump and try to run that way to see if there is a restriction in the tank pick up or pick up line.
 
Kim,

Advance Auto has the correct pump if needed. I picked up an Airtex Model E8016S from them 2 weeks ago for I think $53.00 + tax. Puts out 2-3.5 lbs. Goes tick, tick very, very quietly. Mounts with one screw/stud on an angle just like the original. Solved a whole bunch of Bugsy's problems.
 
I wonder if there is a rubber fuel line that has gone bad internally or a fuel filter that is pluged. Otherwise it must be junk in the tank.
 
Hi Jack! Today I bypassed the fuel pick up tube and line by inserting a fitting with a barbed nipple on it into the fuel tank drain hole and running a fuel line directly to the pump. The car ran a little better, but still is running out of gas in 5th gear after a mile or so. I plan on trying the volume test at the carbs by seeing how much gas goes into a large container in a timed test. I'll let all know the results of that test.
Charlie
 
I really am out of my depth here but, a couple of thoughts.

mine was running out of gas by revving and when I took it in, there were 3 things.

1. the oil in my carb pot was too light and

2. the timing was out - though I don't know what direction the mechanic took it - though I could check.

3. the carb is too big for the engine (adding an SU to a 1500)

I don't #3 is the issue but if you check 1 & 2

also, re: timing, this might be an issue with the vacuum advance since it only seems to happen in 5th and presumably higher revs.
 
How about the fuel filter, is there one at the fuel pump or/and up front in line? Are they clear? Some elec pumps have one kind of build in.
 
The fuel filters are the large metal ones that clean the fuel down to some absurd amount of microns. There is one before the pump and another before the carbs. I bypassed one yesterday and will try to bypass both of them next week. I'm getting away from the coastal heat this weekend and going to the NC mountains. I'll check back in with the results next week. I have yet to do the volume test. All that will be next week.
Thanks to all the replies.
Charlie
 
So, what was the outcome? Inquiring minds want to know.

walter
 
I would really recommend NOT taking the fuel filters out of the system!
Replace both of them with those $1.00 plastic cheapos at the O'reileys parts counter and see if it helps. It could be that your filters don't pass enough fuel but taking them out of the system is not the answer (even for a test because then all of the crud in the system will hit the pump/carbs at the same time and really cause problems!!!)
Bill
 
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