63 FI stalls under load

[Edward G.]

I need help with my 63 FI car. The engine will start good and will idle good at 800 rpm (better at 900 rpm). It will rev up good and is responsive to the throttle. When I put it in gear and let out the clutch (slowly) the engine dies. I can get the car to move by feathering the clutch and working the throttle. It's like I am starting out in 4th gear. I tried starting out in all the gears and that does not help so I believe that I AM actually in 1st gear. I adjusted the timing for 35* total advanced that helped a little, I can now back it out of the garage. My driveway goes down hill so I backed it down the driveway and tried going back up. It made it up the drive but doing the bucking bronco all the way up. When the engine stall it starts up no problem. When I take the plugs out they are all sooty black. Is this a Fuel problem or mechanical like of a tooth on the timing gear.

Ed

[Bob R.]

Re: 63 FI stalls under load

Do you know the ratio of the rear differential. If you have a 3:08 it would make the car difficult to launch.

[Edward G.]

Re: 63 FI stalls under load

It does have a 3.08 differential gear. My driveway is 150 ft long, I would think that once I get the car moving it should go. I have had many standard shift cars in my day and it might jerk on take off but after 20 feet is should go , but I will put that on my list to try.

Thank You
Ed

[Don H.]

Re: 63 FI stalls under load

I assume you have a 7017375 unit. If it is did you check the cranking signal valve (black plugs)? Good luck, Don H.

[Paul Y.]

Re: 63 FI stalls under load

Before you go into the F.I. I would make sure that your electrical is in groove. I have put 100K plus miles on my 63 F.I. with minimal troubles. I agree about the cranking signal valve and it can easily be checked by clamping the vacuum line into it with a small vice grip after it is running. If it smooths out, there is your problem. John, the F.I guru told me the repo CSV are all questionable. What about the fuel filter. Has it been changed in a timely manner? The ignition points and dwell would be the first thing I would check.

[Arland D.]

Re: 63 FI stalls under load

Ed,

Is this something that just started happening all of a sudden or has it been something that has gradually gotten worse? Has there been any work done on the fuel, electrical, or vacuum system? Has the car been sitting for some time?

[Edward G.]

Re: 63 FI stalls under load

The cranking signal valve leaks down faster than it should leaks at 6 seconds instead of 8 @15". If that would give me sooty plugs then that could be my problem. If I pinch the hose would I see better performance under load. I tried that and I really didn't see much difference. The engine idles pretty good a little lopey and revs fluctuate 50 to 100 rpm. I thought that is because of the cam.
Dwell is set at 32. I pulled the distributor and verified gear dimple

Ed

[Edward G.]

Re: 63 FI stalls under load

I rebuilt the engine years ago and have not driven it since. I have started it occasionally and let it run for a while but have not driven it. When I relocated I had to drive it on a trailer and noticed it lacked power. fast forward to now and it lacks power. Fuel filter is new, fuel line from tank is
new, engine fuel pump has been cleaned, Hi pressure pump has new seals. Vacuum at 800 rpm is 12.5.

[Edward G.]

Re: 63 FI stalls under load

Some more info, I had the FI unit off the engine and tested the injector flow rate and it seems ok to me,all of the injectors a shooting and the flow volume increases when I apply oral vacuum to the main diaphragm. The spill valve is free and seems to be functioning properly (so I say).
so now I am stumped.

Ed

[Duke W.]

Re: 63 FI stalls under load

What are your top gear revs at 60 MPH?

What tire size is installed?

What brand and number spark plugs are installed?

Duke

[Edward G.]

Re: 63 FI stalls under load

Duke,

No idea how many revs at 60 mph. I guess I could jack up the rear end and rev it up in gear.

The tires are repro 6.70X15

The spark plugs are AC 44R

Ed

[Duke W.]

Re: 63 FI stalls under load

Does the tach work? If so just find a road where you can do 60 in fourth gear, record the tach reading and post. It should be somewhere between about 2350 (3.08 axle) and 3450 (4.56). Then use this formula:

axle ratio = revs @ 60 MPH / 760

760 is the number of revs/mile for OE 6.70-15 tires.

... never heard of an AC 44R. There is a R44, resistor type (OE engines did not use resistor spark plugs until 1969) All Corvette engines used for normal road driving work best with AC heat range "5" one heat range hotter than OE on small blocks and two on big blocks. If you insist on AC buy a set of R45 and install them. If you're willing to use another brand the NGK B4 and Denso W-14U, are good choices, non-resistor and same heat range as the out-of-production non-resistor AC 45.

Duke

[Edward G.]

Re: 63 FI stalls under load

Duke,

You are correct , the spark plugs are AC R44. If I go with a hotter plug will that help with my stalling problem. When I let the clutch out the engine stall out but will restart with no problem. If I work the clutch and the throttle I can go but the the car bucks like a bronco (horse not the car).
In it's present state I am hesitant to drive it on the road. I am wondering if the problem is fuel related or mechanical. Since I rebuilt the engine I might be off one tooth on the cam timing, or would a weak cranking signal valve cause it to stall.

Ed

[E B.]

Re: 63 FI stalls under load

Ed remove the air filter and try it that way...Ed

[G B.]

Minimizing unknowns

Ed -

I doubt the rear end ratio is the root cause of the problem you described. Anything lower numerically than a 3.70 is certainly going to reduce performance around town, but it won't provide enough of a load to kill the engine during a normal clutch engagement.

I believe it's possible to get some good advice over the internet. There are many on this Forum who are willing to help. To speed up the process, however, I suggest you minimize the basic unknowns up-front. For example, have you ever witnessed this particular fuel injection unit and distributor running (and driving) properly on a stock engine? What has changed since then? For that matter, did you have your own engine rebuilt with a stock camshaft and lash? Have you run a compression check? What is your initial timing at idle with the vacuum advance disconnected?

Has any professional ever worked on your FI? If so, have you asked them for advice? What did they say?

Jerry