I am finishing assembling a 7017320 unit that I bought in pieces. Today I tried to flow test it and did not get a spray until I held the enrichment lever against the economy stop. (I was applying vacuum to the main control diaphragm.) My first thought is something about the spill valve. Any suggestions? Thanks, Don H.
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Re: Fuel Injection problem
Hi Don, You may have hit on something there when you said it could be the spill valve. In theory the spill valve is the accelerator pump.
Long ago one of the old timers named the 7320 spill valve the good guy. Now I am not trying to be demeaning to him but I have always called it the bad guy.
To do a flow test the Corvette Servicing Guide St12 manual says to apply oral vacuum to the main diaphragm. I haven't read that section for a while but I believe I am correct. What that means is you must suck on the main diaphragm doing exactly what you show in your first photo.
Here is what happens when you do that. You suck on the brass T fitting via a long piece of rubber hose that you have to put in your mouth. This causes the main diaphragm to lift which in turn swivels the internal linkage aka axle link. When the axle link swivels it operates the spill valve and gas will squirt out the nozzles in a consistant spray. If there is issues with the spill valve such as a stuck piston, etc then the fuel spray will either be zero or very poor.
I highly suggest the thumb tack style spill valve. Old timers will tell you that the good guy spill valve gives a better idle. Well I am old now and I do not agree. All it does is cause comebacks and grieve.
This is not to say that is you own an FI that has this good guy spill valve in and it's working good that you should replace it. If it ain't broke then don't fix it.
Did you tighten up the screw on the ratio roller assembly?
Did you install the anti-siphon valve in the fuel meter?
Could the check valve in the spider be sticking? If so then that is your problem.
What do you have in the choke housing for a filter? This has nothing to do with your problem but it appears you have a welsh plug? If so remove it and put in a felt filter otherwise you will fry the electric choke cover, etc.
Do you have your drill rotating the correct direction which is clockwise.
What about the siphon breaker kit. I see a wire coming out the back of the unit. Some of the siphon breaker kits needs 12volts for a flow test and one in particular does not.
If you need tech help on the phone get ahold of me. A 7320 unit is a nice reliable Fuel injection. Good luck, John
Did you install the aluminum nut holding the main diaphragm on? -
Re: Fuel Injection problem
John, Thank you very much for the quick reply, you are always willing to help. It has a "thumb tack" spill valve, I put a new anti-siphon valve in the fuel meter. I am pretty sure I tightened the ratio lever and the main control diaphragm (old age . . . ). I did NOT check the valve in the spider, just put air through it. The choke housing does have a felt filter, I ran the air meter on my '60 so it should be OK. Yes the wire you see is for the anti-siphon solenoid, I wouldn't run a unit without one, I experienced hydro-lock about 25 years ago (see attached picture of a bent GM "pink rod"). It does flow when I hold the enrichment lever against the economy stop. I will pull the spill valve tomorrow. Thanks again, Don H.Last edited by Don H.; June 18, 2011, 10:52 PM.Comment
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Re: Fuel Injection problem
Don, I'll ask the question that NCRS does not seem to want to deal with - what's the VIN of your car, ie, is it before/after when the 7300 unit was replaced by the 7320?Comment
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Re: Fuel Injection problem
Hi Loren, Of course it will be numbers matching. Actually the unit is going on my '65 coupe to make it so rare that GM never made it, F.I. with auto and AC! I had hoped to have it on for the road tour to the Novi Convention but I don't think that is going to happen. Maybe next year, Don H.Comment
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Re: Fuel Injection problem
Don,
Follow my thinking here.....
A factoid: When the ratio lever is on the power stop, the main diaphragm will have to rise farther to achieve a given amount of spill valve closure than it does when on the economy stop.
That you get flow only when the ratio lever is on the economy stop suggests (to me, anyway) that the main diaphragm can't rise high enough to adequately close off the spill valve. i.e. something is limiting its travel.
What could cause that?
Well, one possibility is that the main diaphragm disc is hitting the inside of the cover. It could conceivably do this if the main diaphragm cover has been repeatedly and aggressively re-surfaced such that the diaphragm no longer has enough room to move.
So, I'd want to examine the main diaphragm cover to see if it could be the culprit.
JimComment
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Re: Fuel Injection problem
Problem solved! Thanks Jim, it was the main control diaphragm. The bozo (me) that assembled it did not install the gasket, only the diaphragm. Does the enrichment diaphragm have a gasket also? I don't see one in the kit. Thanks again, Don H.Comment
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Re: Fuel Injection problem
Don, You are funny. Jim Lockwood did say a mouth full though. Those main diaphragm covers are typically warped big time between the screw holes. Guys sand the crap out of them on a surface plate (I hope) and then you end up with a really thin diaphragm cover. Gail Parsons taught me years ago to cheat on that issue by putting on two gaskets. But today we have new covers so I just replace them.
Glad you figured out the problem.
Enrichment diaphragm cover gasket. RP never felt the need to put provide for a gasket there. Now I wish they did but what do I know.
Just lap the cover and the backing plate flat on a surface plate (not a sheet of glass or a hunk of your counter top) and you will be set.
Getting back to the main diaphragm cover. I never overtighten the 8 fillister head screws holding the cover on. Doing so will warp the cover again. I just put them in snug and quit.
Good job Don.
Glad you have the thumbtack style spill valve. Anyone want to see this part and the original just look for nice photo in Corvette Servicing guide. JDComment
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Re: Fuel Injection problem
Hi Loren, I always thought that anyone that bought a new 59-60 Corvette with a left over 57 FI unit on it got a raw deal. It's an OK unit at best. The 7320 unit is much more reliable than a 7300 unit.
For those of you that don't know.
Rochester Products had a huge inventory of left over 57 FI units. They made a ton of service replacement units called 7014800R. So they retrofitted a new air meter on the 57 unit, retagged it (not a neat job) and changed the plumbing (vac. lines) and used up some inventory.
But you didn't ask all this Loren. You just asked about time frame but I felt the need to ramble on as the 7300 FI unit is not one of my favorite.
It's not NCRS' fault on the 7300 unit versus the 7320 unit Loren. It may be my fault as I was once given the job assignment by the team leader (along with others) to make corrections on the 58 to 60 FI units.
At the time I had contacts with Rochester Products employees. I couldn't get any concrete info. Brian Futo didn't really know either. Didn't know when the 7320 unit replaced the 7300 unit. Tru story. JDComment
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Re: Fuel Injection problem
As far as I know, this is all 4 of the versions of spill valves that were used 57-65. Of course, the bottom one (latest version) is the "Thumb tack" style. The third one is the better of the two sleeve types.
THE TOP ONE WILL ONLY FIT THE SAND CAST FUEL METERS, The remaining valves are interchangeable in any of the die cast fuel meters.
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