fuel injection set up without manometer ?
 

I just recently put my injection back on the car after a recent motor rebuild. What can I do or not do without a manometer for fine tuning.
It seems to run fine right now except for some slight idle changes that I think might be from a small vacuum leak.

I guess my main question is do I need a manometer ( and someone that knows what the hell to do with it ) or can the unit be set up without ???:confused:

If it runs fine except for some slight idle changes that may be due to a vacuum leak, a calibration with a manometer and fuel pressure gauge won't fix that. Calibrating a unit only sets fuel pressure and gives you a base to other adjustments that may be required. In other words, it "tells you where you're at so you know where to go".

I'd resist the temptation to start fooling around with the rich and lean settings on the fuel meter until all other resouces have been exhausted.

I'd speculate that if you calibrated a brand new unit in '65, drove it awhile and then parked it until now, you could get in it and drive off with at the most, new rubber, seals and gaskets. No recalibration necessary unless there developed some internal blockage of some sort.

What year is your unit and what is it doing? There are a couple people on this board that could help you. This isn't one of those hot restart problems, is it?

i've never had a manometer (never could afford one....), but you can think of the economy and power stops in the same terms as you would a carburetor: if the fuel setting is too lean, then you will have a 'lean surge' at light throttle, if it's too rich, you will only notice it upon acceleration and i can only guess that it would manifest itself as a bog caused by too much fuel.

BUT, as Mike said, you shouldn't really have to mess with it them......

the biggest thing is setting the idle mixture and idle speed, and it should be done in a certain sequence. i suggest the following, in this order:

1. get it to idle at the lowest practical rpm, 850 would be great.... (with the vacuum advance disconnected and plugged)
2. check/set distributor dwell
3. set the timing to the factory spec, with the vacuum advance disconnected and plugged.
4. reconnected vacuum hose to can
5. use a vacuum gauge to adjust the idle mixture screw on the air meter to the highest vacuum reading (connect the gauge to the vacuum advance hose using a 'tee' if you like)
6. adjust the idle using the LARGE idle air screw, do not touch the idle mixture screw

Bill

Mike,

When I purchased the car years ago it had a completely chromed injection unit on it. I have recently undergone a frame on restoration and decided to ditch the chromed unit and replace it with another unit if I could find one close to mine.

I did find one, bolted it on and it runs ok (Supposedly a completely rebuilt unit)...Being in Mass with the weather and the restoration not complete with the wheels still off the car I have only run it while on jack stands.

Sounds good, have to go 1/2 way with accelerator to get to start but does fast idle at 2200 when started and will kick down to about 900 when warm. Wont start hot unless 1/2 throttle again !!!

I just don't want to chase anything if I don't have to...Your advice on not having to re set with a manometer is helpful...hopefully it was done when rebuilt !!!

Thanks

Thanks Bill,

I used some of the information you sent me the other night when I first re started.

So the economy and power stops are where the adjustments one would make with a manometer if needed ?

I agree completely with MikeM and Fuelie65. One of the last things that needs to be considered is the setting of the rich/lean stops. It's really not possible to make these adjustments even near accurately, especially the rich stop, without a manometer. It may be possible to set the lean stop using an old exhaust gas analyzer but that's really not getting the job done and there are other causes of a too rich/lean idle.

The idle mixture adjustment screw on the air meter would be the 1st place I would head. It may seem too easy and uncomplicated but at idle, much of the mixture is controlled by that adjustment. Make sure the engine is at full operating temp before attempting to make any mixture adjustments. Much more critial on an FI unit than on a carburetor.

One very common cause of "idle speed dropoff" on the 380 units is the vacuum advance and the very light springs on the mechanical advance weights in the distributor. If, by chance, the weights are actually partially off their base at idle, the timing will be advanced slightly at the normal idle speed that you have set. eventually, the weights pull back in and the timing drops a few degrees, causing the idle speed to drop a few RPM. In the end, the weights come back to their stop and the engine now idles at a few hundred RPM less than your original setting. For a test, you can secure the mechanical advance weights to the rest positopn with a rubber band, then see if you have the same original idle speed.

There are several more possible causes of the problem that you describe but the above would be likely the most typical. Vacuum leaks are in the running also. Hope this helps.

FI does not start like a carburated car as there is no accelerator pump to give it a squirt of gas; when cold, you hit the pedal one time to set the choke and fast idle cam, take your foot off the pedal, then crank until it starts itself. however when hot, you have to hold the pedal about 1/4 - 1/2 down to keep it from flooding then blip the throttle a couple of times to clear it out until it settles down and idles (particularly important with the new gasolines).
Bill

Hi Bill,

I have tried to start cold by depressing the pedal to the floor once. It does set the choke and fast idle cam but still wont start unless you open the throttle about 1/4 to 1/2 way ???

everything else seems ok, microswitch, choke adjustment etc ...

sounds like the enrichment circuit at cold start is giving too much gas, but i'm not sure how to adjust that (if it's even adjustable) on the later unit. but i THINK that's what the microswitch is for.
Bill

When dealing with old Rochester FI units as far as hot/cold starting, it seems many units stray from the recommended procedure, although the 64-65 380 unit is probably the best for stating. If the engine is ambient temp, but that temp is above 65*, it may be normal that the engine doesn't require the additional shot from the fuel pump by pass circuit.

Check to see if the micro switch "clicks" after about five or ten deg of throttle bellcrank rotation.

Is this cold start symptom your only problem? If it is try this: Don't set the choke by opening the throttle. Don't touch the throttle. Just hit the key and see if it starts. It should fire instantly. Maybe die but see if it hits. This is for COLD START only.

I'm sure you know that holding the throttle down 1/2 way trips the switch to the fuel enrichment solenoid to cut off the fuel shot you would normally get on a start with a closed throttle.

You mentioned a micro switch but just checking to see if you have a cranking signal valve or a fuel enrichment solenoid?

Another way to calibrate it is to buy some dyno time on a dyno that has a good wide band probe to give accurate A/F ratios. Your A/F will be plotted for the duration of the pull and you can then adjust the power stop in or out and do another pull till you get it dialed in. This method calibrates your unit under power which is what you want and it is very accurate and easy. Once set you shouldn't have to tinker with it again. Before you do any calibrating, make sure your entire ignition system is in top condition and the proper distributor centrifugal and vacuum advance curves are in place.:cheers:

Seems like you all have the issue completely covered men. :thumbs: One last comment, give up that temptation to play with the ratio levers as they appear to be ok. :D

What K2 says!!!!

you might have a "leaker"
 

Starting a injected engine when cold is the essence of simplicity: turn the key until it starts.

The fact that you are having to treat the cold engine as if it were a hot start strongly suggests to me that the unit is siphoning fuel into the engine when the engine is off. This is a SERIOUS problem that can lead to engine damage, typically a bent connecting rod.

Before you twiddle with any adjustments, it would be prudent to find out why the normal cold start procedure doesn't work. One thing you might try (and I would) would be to remove the unit from the engine and set it on something.... couple of blocks of wood.... so you can watch the nozzle outlets. Are they dripping fuel? If so, you've got a "leaker" because internal check valves in the fuel path are no longer doing their jobs.

I'd check this before doing anything else to the unit.

Good luck,
Jim

I know this is an old thread, but I have something VERY important to add: Once the FI stops are set right, they should not have to be moved more than 1/6th of a turn. I have often seen some expert advise "Give it a couple turns" on the stops. If you ever hear that advice, don't take it. I thought mine was running OK till I put it on a chassis dyno. Turned out to be very rich and picked up 90 HP with a lean out. If you are near a chassis dyno, use it. Best $90 I've ever spent. Forget about using a manometer. Won't get you anywhere near as close as a dyno. My engine liked 12.9:1 A/F ratio best.

For making rich/lean stop adjustments on a running FI engine, especially when running on a dyno, this is the cool tool to have. Sure beats fighting a darn Allen wrench. Although, you have to furnish your own Allen bit. :thumbs:
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Tom Parsons

Nice pictures but where did the tool come from?

Tom, how do you retain the bit in the holder? The bits that came with mine were magnetic.... they stay in by themselves. But the bit I use on the fuel meter set screws isn't magnetic and I use a dollop of goop [technical term] to keep the bit in place. You got something that works better?

Jim

Jim,
Nope.
I use the same technical substance that you use (but maybe a different brand name) to retain the Allen bit. :rofl:

Tom Parsons