I'm still working on the twisted off cable problem and a friend who is a diesel pump guy looked at the pump and wondered what the little hole in the backing plate is. We think this is a relief hole. So i'm wondering if the backing plate can be installed incorrectly on the suction side rather than on the discharge side of the pump gears. It looks like the backing plate can be installed either way. I believe mine was installed 180 degree out of phase on orientation, rendering the relief non functional. The unit runs fine and I would think for street applications you might not even notice the problem but for racing this really twists off cables. The suction is on the bottom. The relief hole is shown in the 5 o clock position and I believe it should be in the 11 o clock position. Now for you engineer types, i'm wondering if I should enlarge the relief hole diameter ever so slightly( .003) given my extended high RPM operation.
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Re: Fuel Injection gear pump relief hole orientation
Jerry,
You may be able to install the end plate so the relief (air bleed) hole is on the discharge (pressure) side of the pump. DON'T DO IT! If you do you will find your motor will not rev above 3500 RPM no matter where you set the power stop. Now ask me how I know.
With the end plate out of position to the point the refief hole is on the pressure side of the gear pump you force fuel back into the bowl (through that hole) that should be going to the spill valve. In effect you have created a second bypass in your injector and will not be able to supply proper amount of fuel required to obtain high RPM.
I found this out the hard way several years ago. Replace the end plate with the relief below the centerline of the pump. Since my little mishap I always scribe an index line on the pump before I take it apart. Back to the garage! Bill -
Re: Fuel Injection gear pump relief hole orientation
Jerry,
After rereading your post I saw your query about enlarging the relief hole. Don't do it. Its there to bleed air from the pump. Enlarging it will serve no purpose. Now I can go back to the garage. BillComment
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Re: Fuel Injection gear pump relief hole orientation
Oh Man! Your killing me. I thought I had actually found a way to solve my cable twist off problem. The cables are new, the pumps are rebuilt perfectly, but this unit can't make it around a lap of laguna Seca without breaking a cable...HELP!!! Is there any documentation that shows this holes orientation?Comment
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Re: Fuel Injection gear pump relief hole orientation
Jerry,
I can find no picture or written description saying the relief hole should be up or down, but I promise you "down" is right. Others will see your post soon and comment. If I am wrong on this I will stand in a corner of my garage and repeat over and over "Bad Bill" until Spring.
One more thing, the end plate may look easy to install with the relief above the centerline of the pump, but it ain't! I had to work at it to put it together wrong and you will also. Since the pump is easy to remove/install try running the motor with the end plate relief hole in the "up" position. Just be careful you don't damage any of the four threads holding the pump together. BillComment
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Re: Fuel Injection gear pump relief hole orientation
Jerry,
Just remembered! Drag out your VOL. 25 number two issue of the Restorer, turn to page 14, there you will find a fair picture of the never-taken-apart pump that was in my 1965 injector. Just to the right of the scribe point you can see (with a little imignation) the relief hole.
I rest my case.
I don't know why you are breaking cables, but the orientation of the relief hole is not your problem. Good luck! BillComment
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Re: Fuel Injection gear pump relief hole orientation
Jerry,
One possible reason for cable brakage may be your assembly method of the high pressure pump. Your pump operates with VERY tight clearances. If you have assembled it dry you may have a "tight" spot causeing drag/binding. With the end plate removed, add several drops of 30 weight motor oil to the gear cavity. Using the drive cable, rotate the gears. This will center everything up and insure clearance. Install the end plate, (you know which way the relief hole goes). Now slowly torque the four allen head bolts to 40 inch pounds while your helper rotates the drive cable. If any binding occurs, stop, back off bolts, add more oil and repeat process.
With everything you have done to correct things, if this doesn't correct your problem then you have insulted Zora greatly at some time in the past! Amends can only be made by selling me your '65 fuel convertable. Good luck! BillComment
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Re: Fuel Injection gear pump relief hole orientation
Hi Bill and Jerry, Don't know whether I should jump in on this post or not as it's on the funny side.
"Relief hole". I have in front of me my favorite hi-pressure pump to work on. One that has never been apart by the bubbas. Still has the lead in two of the allen head screws with old JB's initials in them.
Relief hole toward the bottom of the fuel bowl.
Low HP pumps have three relief holes- 2 different sizes. HHP powers have one relief hole. Now I am not a racer and don't try and re-engineer stuff so I leave the pumps as stock. Do you know they are over -engineered anyhow from AC and RP.
Do you know the service replacement pumps had more gear clearance than the assembly line ones?
Meanwhile I know this isn't the place for it guys but old JD is in need of two end plates and doesn't care if there is one hole or three holes in them.
More important than the end plate is the spacer between the plate and the pump housing. Always make sure the big hole is pointingtoward the engine.
Story: Yesterday I was having trouble with a hi-pressure pump that bubba scribed with the letter V. On the pump housing, the spacer, and the end plate he had a nice V stamped. The dummy must not have had a china marker.
Anyhow turns out the spacer was 180 degrees out. Whew!!!
If you really want to learn how to assemble a pump without looking at the previous rebuilders scribes you need a huge set of pin gauges like FI Art has.
You need to measure the size of the two big bores for the drive gear and the idler gear. The drive gear bore is a tad bigger than the idler gear.
That way you can tell what orientation the spacer should be and therefore ignoring the novice before you.
One of you out there working on pumps is using a huge chisel to mark the pump.Whew!!!! Go to Office Max and buy a China Marker or write me and I will buy you one.
Note: Do you know you can install the pump to fuel meter bowl gasket on backwards? Yes and it will not leak fuel. But you will have very little pump pressure cause you blocked off the pressure hole with the gasket.Comment
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Re: Fuel Injection gear pump relief hole orientation
You are correct. I have now been overwhelmingly convinced by people I have great respect for that the hole is where it should be. I am really frustrated here. Hauling a race car over a thousand miles through the mountains only to have cables break after a few laps is really really frustrating. I have been trying to solve this problem for two years and getting no where. Other racers are running this setup and twisting their motors to the same RPMs and not breaking cables. THe pumps have been rebuilt by someone I have complete faith in . The cables are the same everyone else is using and the pumps are good. To my way of thinking it must be something downstream of the pump that is introducing higher than design loads on the cable. I am completely open to ideas. I am frustrated and worried that I will have to go to Monterey this year with a carburetor on because I can't solve a basic problem. How humiliating.
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Re: Fuel Injection gear pump relief hole orientation
are you nusing the cable only or the cable and its housing? if you are using both, try using just the cable. good luck and stick with mr rochester,fi. mikeComment
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Re: Fuel Injection gear pump relief hole orientation
I have spoken to the cable manufacturers and engineers in this country and in united kingdom. The housing is an integral part of the design and is there for dampening and support . Harmonics are a problem in severe service. I know you can run without the housing and I have done it. It doesn't help the cable breakage problem in my case and in general I would not recommend based on the engineers recommendations.
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Re: Fuel Injection gear pump relief hole orientation
I heard from a good source that sometimes a flaw in the housing can cause a cable to fail and it was suggested when I put in a new cable I also change the housing.
Did you use the same housing for all the broken cables?
Just a wag....Comment
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Re: Fuel Injection gear pump relief hole orientation
Joe I appreciate your idea, I am looking for anything that could be problem. I have run with two different housings and without housings. I've run with synthetic lubricant and with dry. I even put Marvel Mystery Oil in the fuel. I'd kill a chicken and dance in circles if I thought it would help. I'm sure this will turn out to be something that I'll look back on a think it should have been obvious but it's not so far.Comment
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Re: Fuel Injection gear pump relief hole orientation
Jerry,
I can't remember if you've answered these, before, but have you tried a different distributor? A different pump? Have you spun the cable up to the rpm's your turning with a drill, or some other way while not running, to see if you can replicate?
How about posting some pictures of the setup. Maybe someone will see something that seems odd, or different with the unit.
You better not show up with a carb, this August. ; )
GeorgeComment
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