Running lean?

[George W.]

1960 FI--starts right up and sounds great when cold.

After engine warms up---starts to sputter. Will accelerate nicely giving gradual pedal, but stumbles when quick WOT depressed.

Engine will not fire once hot (using proper hot start-up procedure---WOT, short crank, wait 20 seconds, crank)

#1, 7, and 2 exhaust ports read apx 380 degrees

#8 reads 570 degrees

Center manifolds (numbers 3,5 and 4,6) read 719 degrees.

exhaust pipes just behind manifolds read 475 degrees.

Do these temperature readings help identify what's going on?

Thanks,
George Wright 210 748 4693

[Joel T.]

Re: Running lean?

George,

I'm certainly no FI expert, others may chime in... Have you checked your dwell and timing? I would do that first. If you have another coil, you might do a quick swap to see if the problem goes away. A flaky coil will give all sorts of strange results, particularly when it gets hot...

Others, more versed in this sort of thing will certainly chime in.

Good luck,

Joel

[Jerry G.]

Re: Running lean?

Running lean on INDIVIDUAL cylinders is not a characteristic of FI. Unless you have dirt in system, but dirt should not "clear up" and then get bad when hot.

[John N.]

Re: Running lean?

Running rich will also put a lot of heat into the exhaust system. Retarded timing will also create heat.
Regards

[William C.]

Re: Running lean?

OK, when cold, you are (should be assuming a 290hp with the correct injection)) running with the choke on that puts the power valve in a full rich condition. Warmed up, it comes off the full rich and leans out the system to achieve "normal" fuel flow based on the signal from the airmeter. Id sounds like when it comes off choke the system is too lean. Your array of temperatures also indicates a rich/lean mixture between cylinders. Has the unit been checked, rebuilt, how recently? has it been sitting for a while? This may be a "one look is worth a thousand reports" issue that can't be diagnosed without a lot more detailed information...

[George W.]

Re: Running lean?

OK, when cold, you are (should be assuming a 290hp with the correct injection))

---Above is Correct---


running with the choke on that puts the power valve in a full rich condition. Warmed up, it comes off the full rich and leans out the system to achieve "normal" fuel flow based on the signal from the airmeter. Id sounds like when it comes off choke the system is too lean.

---On initial "cold" start up, the engine/unit will run nicely. As it warms up, I can take it out of "choke"/fast idle mode. At this point she idles smoothly at 850/900 rpm, allowing me to check dwell, timing (idle 16/18 degrees and total at 3000 rpm 34/36 degrees), and play with idle mixture/speed. Engine revs up with great response.

After 15 to 20 minutes of run time she starts to stumble, idle decreases, and even when put on fast idle, will eventually "quit". No restart until cool.


Your array of temperatures also indicates a rich/lean mixture between cylinders.

----Is there a "guideline" for temperatures I should be seeing, and variances?


Has the unit been checked, rebuilt, how recently?

---newly re-built by one of the best.

has it been sitting for a while?

---No, have been running unit daily since installation.

This may be a "one look is worth a thousand reports" issue that can't be diagnosed without a lot more detailed information...

Additional information:

---"097" cam, have double checked lash, 12" manifold vacuum, economy to power stop seems to be operating properly. Good wires, rotor, cap, points, condenser, coil, re-worked all electrical connections and grounds, distributor re-built at time unit was done.


Went out and got another set of spark plugs (Autolite 295), and 5 gallons of Aviation 100. Will empty fuel tank and add the 100 octane and try again. Hope to report back later today.

Thanks to all who have offered ideas/thoughts/questions,

George

[Joe C.]

Re: Running lean?

Two more possibilities which assume the Rochester unit is OK:

1. Vacuum leak when engine expands with heat.

2. Coil overheating with engine temp.

[George J.]

Re: Running lean?

If you try a new coil, also swap out the condenser. I had a situation, once where I replaced the coil, but then the car still didn't run completely right. It turned out that the condenser was bad, too.

[George W.]

Re: Running lean?

Okay,
Got the Av gas in the system. She sounded a little better, but problem persists. Unit did fire upon first "hot" restart attempt, but died and has not fired since.

Coil readings: 1.3 primary cold-----------1.5 hot
8.18 secondary cold------10.4 hot

Vacuum readings: 1,800 rpm = 12", 1,200 rpm = 10", 850rpm = 9"---These readings remained the same from cold (80 degrees) to hot (180 degrees).

Someone mentioned condenser---dist. is rebuilt with new points and condenser. Resister on firewall has 12v in, 5.7 out (if I remember correctly)?


????
G

[William C.]

Re: Running lean?

George, with all due respect, the vacuum readings at 1800 for sure indicate a major problem. should be well over 25 at no load 1800 rpm. have you tried pulling the injection unit off and testing it by looking at the flow pattern from the nozzles for consistency? The process is outlined in the service manuals. I don't think I'd try it with gasoline, but I think stoddard solvent is non-flammible and about the same specific gravity as Gas. Check the archives for more info.

[George W.]

Re: Running lean?

George, with all due respect, the vacuum readings at 1800 for sure indicate a major problem. should be well over 25 at no load 1800 rpm. have you tried pulling the injection unit off and testing it by looking at the flow pattern from the nozzles for consistency? The process is outlined in the service manuals. I don't think I'd try it with gasoline, but I think stoddard solvent is non-flammible and about the same specific gravity as Gas. Check the archives for more info.

William,
I've had the unit off and performed a flow test. This was a few weeks ago.
I was trying to rule out all other possibilities before going through this test again.

Can you tell me what I'm looking for if my vacuum is too low at 1800 rpm?

Thank you,
G.

[William C.]

Re: Running lean?

Unequal flow at the injectors...Same problem as identified by your IR gun readings. If you have a service manual, I believe the process is shown there or in the FI supplement.

[Jerry G.]

Re: Running lean?

If you think theres a vacuum leak why chase injector flow. Seems like a complete check for a vacuum leak is in order first.

[George W.]

Re: Running lean?

Okay,
Performed a flow test:



All nozzles have nice steady stream; I do not have the ability to test pressure.

All intake runners were "wet" with fuel.


But, when applying oral vacuum during flow test, there was not a complete "shut off". Also I could blow through the tube and air escaped at the air meter. I don't think this is supposed to happen?

Noticed another oddity. What looks like brass "filings" from the fuel pump drive cable (see photo below).



Next photo shows old (broken) drive cable---it's steel. Are the new replacement cables made of a different material?

Also notice the much thinner flange on the new (brass colored cable).



Found another surprise (remember, the distributor has been rebuilt).

End play in shaft is .026 even with a couple of shims installed.








Thoughts?
G.

[Joe C.]

Re: Running lean?

Thoughts?
G.

1. I'm no expert on Rochester units, but unless the flowmeter diaphragm passage seals on installation, I would think that the diaphragm is ruptured. Is there a passage that gets covered or sealed when it installs on the plenum?

2. The end play on distributor shaft, although excessive, won't disturb the timing since the shaft pops up and stays there while running. When shutoff the shaft drops down and will "advance" the timing. The end play should be max .008" and I like to shim them to .002" - .003". I'd find another distributor rebuilder, or do it yourself next time.