MFI, 1972 warm-up issues (combined)

[bkreigsr]

you are getting forced hot air blown onto the thermostat from the heat exchanger right? check for splits in the hoses?
bill k

[jluetjen]

Originally posted by SandyI

On a cold start up, the hand throttle fully up will keep your car idling at about 900-1100.

Huh??? If I left the hand throttle full up after cold-starting my car I'd have the engine bouncing off of the rev limiter. When I start it I usually pull it full up, after that I have to adjust it somewhere in the middle of it's travel depending on the temperature of the engine.

BTW -- My 69E (with MFI) runs smoothly when cold and using the hand throttle to keep the idle at about 1000 - 1500 RPM.

[Bobboloo]

Originally posted by wahoofan

Now, here's the questions:

1) Am I hurting anything on the engine by forcing it to run so poorly in the cold with cold oil, etc.?

2) Since I won't be able to get into much hard-core analysis of the MFI 'til spring, is there any quick-fix or "smoking gun" to chase for this problem? I have already cleaned the thermostat and checked the hoses, new fuel filter, new oilfilter and change, new air filter, new plugs and wires, new cap/rotor/points, new battery.

1) No you won't hurt the engine.

2) It sounds like your cold start system is working. The cold running isn't right though. I don't see a quick fix here. Troubleshooting with CMA would be the proper procedure.

Clean all the contacts of the connectors for your engine harness. Particularly the CDI wires and the 14-pin connector. I know the problem doesn't seem electrical but connectors expand when they warm up and if one has corrosion it will not make good contact particularly when it's cold. This won't cost you anything and should be done anyway considering the age of your car.

Keep in mind too that the problem can have more than one source so that's why CMA is necessary for proper troubleshooting. It could be caused by injectors, check valves, electrical etc.

[SandyI]

Originally posted by jluetjen
Huh??? If I left the hand throttle full up after cold-starting my car I'd have the engine bouncing off of the rev limiter. When I start it I usually pull it full up, after that I have to adjust it somewhere in the middle of it's travel depending on the temperature of the engine.

Your rev's instantly jump to the limiter on the first cold start of the day in the winter? If your hand throttle sends your rev's to the limiter, you should have it adjusted.

Mine climbs toward 4000 rpm once the engine has a bit of heat in it. But it doesn't get near the red line.

[Lukesportsman]

My MFI actually starts better if I hit the key with the hand throttle all the way down and soon as it catches I lift it about half way up. It actually has trouble starting if the hand throttle if lifted off rest before it ignites.

[wahoofan]

John,
Here is a pic of my t-stat before I reinstalled it. Look about right?

[Grady Clay]

For reference here is the previous thread:
”MFI, 1972 warm-up issues (combined)”

OK, let me try and clarify the symptoms:

“Car runs great when it is warm - seems smooth with lots of power and idles around 800-900...”
Good. That probably means the mixture is only slightly rich and the thermostat is turning off.

“…fuel odor when you stop at light if you've been on it hard, no strong fuel odor at idle.”
Is this gasoline smell or rich (unburned hydrocarbons) exhaust smell? First check all the breather connections in the trunk and make sure some fuel line isn’t leaking. Is the fuel level sender gasket OK?

”When cold, car is a bear to get started and runs awful for 3-5 minutes.”
You need to check and see if the cold start solenoid on top of the fuel filter console is operating (and turning off).

”The car turns right over and catches right away…“
This indicates there is cold start enrichment – can be cold start enrichment or thermostat, should be both.

”…but it won't stay running unless you hold the pedal about halfway down. During this period of sputtering and clunking it will stall if you try to give it too much gas.’
Usually this is a lean condition but in this case it can possibly be very rich. If rich the excess fuel is cooling the combustion process and you have to open the throttles a lot to pass the gas out the exhaust.

”Then suddenly, after a few minutes, it seems like it will catch and rev freely and smoothly and will idle at a real low rpm.”
The characteristic is the sudden transition to better running when the combustion chamber (spark plug) gets some heat.

”Once it warms a little more idle will rise and the engine will run smoothly.”
Normal (but too rich) operation.

Am I correct with each of these symptoms? Is there anything to add?


Bobby (Pelican Bobboloo) and John (Pelican john_cramer are right on the mark.
It would be beneficial to re-read our discussions last fall and review the links.

The critical issue while diagnosing is to not dilute the oil with gasoline.
In this process you may have to change the oil several times and replace the spark plugs many times. Don’t throw them away. Once you have it running correctly, you can reinstall them and they will clean right up. This time of year I would start with some NGK BP5ES plugs. Just don’t use them for full throttle runs or highway – they are too hot for that but will work well for diagnostic purposes. Use BP7ES or BP8ES when you go out for runs. Remember – fresh premium gas, siphon/pump old gas into another car.

As I said last fall, it is very beneficial to run the 911 on the highway and some “spirited” driving during this process.

Check & Measure first, Adjust after.
CMA, CMA, CMA2….

Best,
Grady

EDIT to correct a typo "cols"?

[wahoofan]

Grady,

Your re-cap of the symptoms is pretty complete.

You asked: "Is this gasoline smell or rich (unburned hydrocarbons) exhaust smell? First check all the breather connections in the trunk and make sure some fuel line isn’t leaking. Is the fuel level sender gasket OK?"

I'm pretty sure it's unburned fuel, as I never notice any fumes in the trunk and all of the hoses seem to be hooked up correctly to the charcoal canister.

So if I try to distill this info down, am I right that the cold start solenoid could be the culprit? What exactly does it do, and how would it being bad cause my symptoms? Also, how would I go about testing it?

BTW - Sorry for resurrecting this discussion with a whole new thread. My biggest immediate concern was if I was damaging the motor, and the concensus seems to be that I am OK as long as I have plenty of OIL in the oil tank(which I do).

[304065]

I only count 24 pairs of discs on that rod, is the last one, at the far right end in the picture, a pair of discs? It looks like a solid spacer.

Cold, rod retracted, fat. Hot, rod extended, lean. Hmmm. . . .there's probably an analogy to Nature in there somewhere. . . anyway, if you are missing a pair of discs this could reduce the rod's range of motion, resulting in a mixture that is too rich when the rod is extended. Just something to check. Also, if you omit the paper gasket, the rod will be sticking out too far all the time, resulting in an overly lean mixture.

[Grady Clay]

The insidious part about diluting the oil with gasoline is the
thinner oil-gas mixture is consumed by the engine at a more
rapid rate than clean oil. The consumed mixture is replaced
with gasoline, sometimes at the rate where the level in the
tank even rises. One run on the highway with the oil up to
temperature evaporates the fraction of gasoline and can
leave the remaining oil insufficient for the engine.

I have seen cases where the owner checked the level in the
tank and 10 miles later up I-70 threw a rod because the
gasoline evaporated.

Of course the gas-oil mixture doesn’t lubricate very well
and that takes its toil on cams, rockers, chains, etc.



A cold start solenoid valve is supposed to shut off when
the power is removed. If it hangs open there is a huge
amount of fuel being added until vibration or whatnot
gets the valve to seal closed.

When testing it you only get one shot when it is cold.
Plan ahead. Get several meters of 4.5 mm hose.
The night before, install it on the outlet of the cold
start solenoid valve with the entire hose running
slightly “up” out of the engine compartment (this is
so the gas won’t drain out emptying the hose). With
a jumper wire, actuate the valve, fill the hose and
confirm flow and shutoff. Let it sit in the cold overnight
and repeat cold in the morning.

The single morning test is important. You want to
actuate the solenoid for 2-3 seconds, confirming flow,
and then see if the valve shuts off completely the
first time. No drips, no runs, no errors.

Do this outside and be VERY careful – you have
open gasoline and sparks! MFI runs very poorly after
an engine fire or worse.



I think I posted a nice procedure for Stijn.

Best,
Grady

[304065]

"Ralph was disappointed to learn that his 928's air conditioning system wasn't up to the task of cooling the 1500 degree gasoline fire caused by a faulty cold start system. 'Shoulda checked it,' he groaned, as his Rolex melted."

Fire is no laughing matter. Gasoline has an energy content of around 45 megajoules per kilogram. TNT has 4.184.

Your 62 liter gas tank contains 43 kg of Gasoline. That's the equivalent of 1017 pounds of TNT. Treat it accordingly.

[wahoofan]

So, if I'm following the gist of this, does this mean that my engine stumbles and sputters because of too much fuel when cold? Does that mean that disconnecting the cold start solenoid before a stone cold start would make it run better initially?

[72doug2,2S]

The previous owner unhooked my cold start and never had the throttle lever hooked up. I've never had these fixed. It takes a while to crank over and I have to hold down the gas to keep it idling. After a few minutes it's happy and going.

What is the symptom of an excessive burn gas smell, rich?

[jluetjen]

72doug2,2S; To be honest you need to get those two features fixed. The fact that the previous owner disconnected them and then tried to kluge the MFI around that fact is proof that your system set-up incorrectly. Previous owners always seem to have been in denial about why those sub-systems were added to MFI in the first place. I guess it's some sort of genetic remnent from the days (mid to late -70's) when pollution controls inevitabley ruined the performance of an engine. In the case of MFI -- it just aint so!

Rather then try to diagnose a system which is incomplete, you really need to follow the "Check - Measure - Adjust (CMA)" process that start with "Make sure that all of the systems on the engine and MFI are functioning correctly.

Are you familiar with the CMA data which is available under Pelican's "Technical Article" section?

[72doug2,2S]

John, I hear ya. Is cranking for more than 10 seconds destructive to anything besides excessive wear on the starter? It fires right up and does not run rough even cold.

My intentions are good and I would like to learn the CMA, but the manual is not written for a novice.

Perhaps Grady will write the book MFI for dummies with lots of step by step pictures.

[Bobboloo]

Originally posted by wahoofan
So, if I'm following the gist of this, does this mean that my engine stumbles and sputters because of too much fuel when cold? Does that mean that disconnecting the cold start solenoid before a stone cold start would make it run better initially?

No that isn't the gist. A stuck cold start solenoid will dump too much fuel into the motor after the initial start sequence. You need it for the start sequence, however, this means that warm running conditions as well cold will have too much fuel after the start and it will dilute your oil and the host of damage Grady outlined will occur. This could account for the gas odor.

There are other causes of gasoline odor. Breather hoses in the trunk can be the cause as well and are likely. Remove your trunk carpet and check them. There are also two that go to a black box behind the dash. Remove the cardboard panel and check those as well.

It's a good idea when working with fuel systems to have a fire extinguisher within arms reach should an accident occur. Having to run into the house to retreive one can cost you so before you check the cold start valve have one handy.

[David E. Clark]

Originally posted by 72doug2,2S
Perhaps Grady will write the book MFI for dummies with lots of step by step pictures.

I'd be willing to pay now if I could get a promise that this would be published. I'll bet there are A LOT more like me!

[donstevens]

Originally posted by David E. Clark
I'd be willing to pay now if I could get a promise that this would be published. I'll bet there are A LOT more like me!

Me too .....

I have a different set of problems. My car has headers and as such no warm air form the heat exchangers going ot the thermostat (I have some new heat exchangers to remedy this but have not installed them yet). My car starts and runs fine and seems to run better when cold. As the engine heats up, it stutters a bit, particularly at part throttle, stinks (I think it is over rich), and gets horrible gas mileage. Is this over rich?

By the way, I did an oil analysis last summer and while the wear metals seemed a bit high there was less than 1% fuel in the oil.

Don

[304065]

Fellas, the book is already written. Grady has posted a ton of threads describing almost every aspect of the MFI system, and if you search, you can find "compilation" threads in which he includes every link!

The thing to do is print them all out and put them in a notebook along with a copy of "check measure adjust" and copies of the relevant pages from the factory manuals.

And don't leave home without it.

[David E. Clark]

You're right John. I have copied everything that I could find with regard to MFI; but the part of the quote I thought would be most helpful was "with lots of step by step pictures." At least for this "dummy." You know what they say:



Look how helpful the pictures are in the 101 Projects book and the engine rebuilding book.