MFI, Im not bringing this back to my mechanic

[Shuie]

A few months ago you guys helped me out with some MFI problems. Long story short, the car was a ***** to start; it had idling problems, and would not start at all when it was hot.

My mechanic was able to get the car running again after a few months in his shop. The car still took a lot of cranking to get it to start, but it would run and idle fine after a minute or two with the hand throttle engage.

I got under the car the other day to check out a few things and I noticed that the heater tubing coming from the top of the shroud and feeding the LHS heat exchanger had been completely severed for a good while. Great. That means that no air has been pushed through the LHS heat exchanger and on to the thermostat on the front of the pump that leans the mixture out as the car warms up. No way am I bringing it back to my mechanic if he didn’t catch this. In fact, I’m a little concerned that he made the car run as well as it has been without this stuff intact.

Anyway, I installed a new heater tube connecting the heat exchanger to the shroud and cleaned the thermostat on the front of the pump last night. I’ve definitely got warm air going to front of thermostat now, and it’s leaning the mixture out as it warms up. Problem is that its leaning it out so much that the car dies. I can use the hand throttle to hold the idle up, but this is obviously not right.

I've been going through a bunch of the old MFI threads again. I’ve also been re-reading CMA. I'll fix it myself this time, starting with the cold start system.

I didn’t find the following in CMA. This is my current cold start fix plan based on some old threads. I just want to make sure I’m not misinterpreting anything I’ve read on how to get around the cold start. Any help you guys can give is appreciated:

Since the car takes so much cranking to get it to fire, I’m thinking the cold start system has been disengaged. The middle fuse from the panel that wiring harness plugs into has been removed, and unhooking the wire from the top of the solenoid on the fuel filter does nothing to the starting behavior of the car. I’m going to unhook the fuel line coming from the top of the fuel filter and stick it in a bucket to see if it dumps fuel when I turn the key. Is there a better way to test this? Also, will a 12volt lead wired directly to this solenoid via pushbutton in the cockpit dump fuel on demand when the car is cold?

TIA

[jdowty3]

I think you should take it back, if only to tell him what you found and fixed. He may offer to adjust the mixture at no charge for such an obvious oversight.

[Shuie]

No way, you guys can help me with this . It's not going back to that shop.

Im getting ready to go unplug my cold start feed line and see if its pumping fuel. Just picked up a pushbutton at the auto parts store.

Kurt? Milt? Mr914-6? p-thomas? Warren? Grady? John Walker?Any other MFI gurus have any thoughts or advice before I burn something down? I have a 25lb halon bottle within reach

Seriously, is that the right way to do the pushbutton cold start device?

[Shuie]

Okay, I just tried what i think is the cold start solenoid. I didnt have a another hose to pull to the outside of the engine compartment so i used this:




I turned the key and let the fuel pump run for a few seconds just like I was starting it. I then cranked the engine for 2 ~30sec intervals. No gas in the bottle. So that means the cold start is disabled or broken, right?




Middle fuse is definitely gone also. One of the wires is missing from the terminal block also, so does this look like the cold start has been disabled intentionally?







This is the solenoid, right? The lead on the top is the one I was going to wire the pushbutton to. Am I headed down the right path, or am I about to screw something up?





Thanks guys!

[Early_S_Man]

Sherman,

Yes, you are right on both counts ... you need that #2 fuse for the cold-start relay AND the Speed Relay to get any +12 Volt power!!!

Any backfiring on over-run since you got it back from the mechanic?

Of course, there could also be problems inside the speed relay causing the fuse to blow ... you have read my 'MFI Warning' thread[s], right?

And, there's always the Thermo-Time Switch, 14-pin connectors, etc., that could be interrupting the signal to the cold-start relay! Or some other oxidized Faston connector along the way ...

[304065]

Hot air hose to the MFI thermostat SEVERED?

I'd work him over with a wet towel.

Smart to use a pushbutton rather than a jumper. You don't want any sparks back there.

[Shuie]

Cool. Thanks guys.

Warren, I do remember reading the thread, but I don’t remember the specifics at the moment. I'll go back and read it again before I do something dumb. I need to print a lot of your stuff out to put in a binder.

I just broke out the volt meter to look for a live voltage source to test the solenoid/pushbutton thing. I’m going to jumper off the top fuse block through the pushbutton to the top of the solenoid to see if I can get it to dump fuel before I wire it up for real. If it works, I'll pull a new wire back there and hook the button up somewhere on the dash.

I also just looked at the fuse/relay panel on my '73 (I’m 99% sure it was MFI originally also). There is a definite inconsistency between the two panels, check the pics below. The wire going from the engine harness to the 2nd fuse on the panel on the '72 has been chopped and taped up and a relay is missing.




heres the one from my '73

[Early_S_Man]

John,

I think he was referring to the big, short 2.25" tube direct form the air shroud ... still means no hot air to the thermostat, though!

Sherman,

Yes, a temporary remote starter switch will work fine connected to the fuse panel. But, it is very easy to wire a permanent remote starter switch and mount it on the electrical panel ... just intercept the #50 Yellow wire at terminal #1 of either 14-pin connector! Connect the other side of the switch to the same terminal lug as the big red alternator wire at the fuse block -- opposite the Red/Black wire on fuse #3.

[Grady Clay]

Sherman,

Sorry to hear this.

Probably what happened the tech didn’t realize the thermostat wasn’t getting warm and therefore not turning off so the main mixture got leaned at lot to compensate. Now that the thermostat is turning off the mixture is too lean to run.

Now is the time for YOU to get the system working correctly. Between the CMA, prior threads and our help, I’m sure you can get it working the best possible. It will take your buying some parts and tools but very worthwhile in the long run.

You are right, take the fire hazard seriously.

The “Push Button Cold Start Enrichment” is one used by many. You only need a little spritz while cranking. It also tends to reduce oil dilution.

Part of CMA which isn’t there is to make yourself a plan of attack. You have been on these MFI threads. You know there are certain things that you must confirm in sequence. How many times have seen someone get to step #27 and found out the problem could have been diagnosed in step #2 that they didn't do?

I know a lot is redundant but if YOU are going to do it RIGHT now is the time to plan.


We are standing by to offer our “lame” and “at distance” suggestions. You are the guy in there with the tester and wrench.


My suggestion is to:
Plan a strategy.
Gather the tools, an inexpensive exhaust gas analyzer being most important. Make yourself a nice main mixture tool and the idle tool.
Forget the electrics for now.
Insure the thermostat is fully turning off. When you think it is off, blast it with a heat gun or hair dryer. If the mixture changes, it wasn’t off.
Get the main mixture back in the reasonable (rich) range, then lean to perfection.
Every time you fuss with the main mixture you will need to keep the idle close to correct.
Of course while doing this you want to insure you don’t have fuel in the oil and the spark plugs haven’t been compromised.
Only then light into the electrics and CMA.
As you get the electrics working, that will affect the running and you will need to re-adjust the mixture several times.

Remember, it pays to be cool.

2c

Best,
Grady

[Early_S_Man]

Sherman,

No relay missing ... you've got the two-stage rear defrost relay -- the 2nd aluminum box over from the black, round relay. On your '73 the single-stage rear defrost relay is the 2nd round one to the left.

And, from your '73 pic, yes it was MFI, and the Speed Switch is still there, so, you have a spare!!!

I'm not sure what to tell you about the 'modified' wire ... but the Red/White wire on the right is the one that needs to be hooked up to either fuse #2, or fuse #3 (Blue/Yellow wire on lower right) -- since I don't think that Sportomatic wire will mind a bit, if there is a problem with the #2 fuse position.

I can't see the taped-off wire in either of the '72 pics ... any chance you can post another pic looking straight at the fuse block with right-side wiring visible???

BTW, there's a MAJOR ANOMALY about the fuse block I need to mention ... it's either labeled wrong, or the schematic bus connections between fuse #1 & #2 should really be between #3 & #2, take your choice. The Sportomatic fuse to the Blue/Yellow wire gets power from the alternator wire alone, and isn't shared via a bus with #2! Anybody ... confused enough, yet???

Just to make it very clear ...

1. Top fuse is to rear window defogger relay via either a large Red or Red/Black wire on the right.

2. Middle fuse is to Speed Switch/Speed Relay/Speed Transducer and the Cold-start Relay ... both powered by the Red/White wire on the right!!!

3. Lowest fuse is for Sportomatic ... small Blue/Yellow wire on the right.

[Zeke]

My fuse block doesn't have a wire at one end of the middle fuse. Yet, when I install the fuse, the cold start fuel solenoid works. So, at least on a '71, there is power to the fuse holder from within.

[Jay Zollinger]

Has anyone tried to install the thermostat replacement/enrichment device that Henry Schmidt sells at supertec performance, or something like it? It replaces the thermostat altogether and uses a pushrod on a hinge hooked up to an extra lever next to the parking brake to operate the rich-to-lean switch in the MFI pump that the thermostat otherwise controls. Henry claims that you can disconnect the cold start system altogether and maintain a lot of control over the fuel mixture--lean it out at altitude, etc.

In theory at least, it sounds like a good idea that could help with a lot of Shuie's problems--couldn't he just put the MFI pump in full lean position and set the idle and part load mixture? I've been thinking about trying this system on my '73S because I'm having a hard time getting my thermostat to cover the full range that I need it to--it's too lean when the thermostat is cold and all of the expansion discs are in place, and just right on start up with one removed, but then it never leans out all the way and runs too rich when it's warm.

I'd love to hear if anyone has experience with the device.

[Shuie]

Thanks again guys. Solenoid definitely squirts fuel if you put power to it. Worked like a charm. No fires either.

I didn’t find any pics when I searched this, so I'll post some of the setup I used for the next guy that searches for this stuff. I obviously don’t know a whole lot about all this so find a better safer way or try it at your own risk. Get a big bottle of this stuff if possible.




I removed the top fuse and connected one wire from my pushbutton to the now dead end of the connection. I actually didn’t realize the other end of that connection was always hot until I put the meter on it with the key turned off . That’s a little scary. I then connected other wire to the top of solenoid, popped the fuse back in place, turned on the ignition to get the fuel pump going, hit the button and watched to fuel squirt into my Nestle catch can.




I brought my wrench a copy of CMA after my car had been sitting in his shop for 3 months. He had the car running within 48hrs of that visit, but he obviously didn’t read the manual. I don’t know what he did to get the car running, but I’m going to go back and start at the beginning as Grady suggested.

More great info, thanks Warren, Grady, and John. I really appreciate the help.

[Shuie]

Originally posted by Zeke
My fuse block doesn't have a wire at one end of the middle fuse. Yet, when I install the fuse, the cold start fuel solenoid works. So, at least on a '71, there is power to the fuse holder from within.

ok, I'll find a fuse and see if it works. Im gonna feel like a dummy if all I need is a damn fuse.

[sundaypunch]

My cold start system has been bypassed and I've got a tiny dash mounted button to give it a squirt. The concours folks might not like it and I wouldn't convert a functioning system, but I love this setup. It does only take a 1-2 second squirt and the car fires immediately. It is such a simple solution if you don't have a show car.

[Grady Clay]

Jay,

On some of my prior posts I describe my homemade replacement for the thermostat on several 2.8s. Just a screw with a lock-nut on a plate in place of the thermostat.

I would like to see some one make a “Porsche Quality” mechanical replacement for the thermostat. It should be adjustable from the cockpit. Not pre-load the pump mechanism by having a spring to load it. Have a no-fail design so it can’t change the mixture while driving. The good news is that in failure mode it can only go rich.

I would never use these kinds of external mechanical things to regulate or adjust the main mixture. The pump has a proper aneroid on top to compensate for barometric air pressure and altitude.

This may be taxing my memory but the Factory delivered thermostat had steel shims in addition to the bi-metal in order to properly pre-load the stack. Perhaps someone left them out of your thermostat.

Let’s not hijack Sherman’s thread – he needs our help.

Best,
Grady

[Early_S_Man]

Sherman,

The one serious reason that the cold-start system may have been disabled is fuel leaks at the cold-start squirters!!! Either the hoses may be original and cracked ... or one or more of the plastic squirters may have cracked or popped out of their hole, and they aren't available, now or ever as replacement parts, thought there isn't any reason that they can't be replaced securely with a bit of epoxy.

The OEM German hose is still available, and the crimps can be replaced by tiny worm-gear clamps. I would strongly suggest that ALL of that cloth-covered hose be replaced with new hose of the exact same type ... I am sure Pelican sells the 4.5 x 9.5 mm hose , 999.180.080.50 by the meter. Two meters should do the job. Be very, very carefull removing the old hose and specifically between the squirters when cutting off the old crimp rings!

[Zeke]

I don't think talking about alternatives is hijacking the thread. I didn't know these cockpit controlled devices existed except for the push button cold start. If we were so pure as to never vary from the original question, not as much will be learned.

I've seen real hijacks. Personal converstions and the like. This is not like that. Thanks for understanding my point of view.

Best,

Milt

[Grady Clay]

Sherman,

Warren is exactly right; all that plumbing needs to be new.

Another cold-start solenoid issue is that, in its old age, sometimes it doesn’t shut off immediately when power is removed. You can imagine the poor running and oil dilution from that.


Warren,

Are the OE hose clamps available? I see them on many cars.

Best,
Grady

[Shuie]

Thanks Warren and Grady, thats kinda what Im worried about. I think someone disabled it for a reason. Apparantly it wasnt becuase of the solenoid. Im going to take a good look at the lines before I hook it back up and blow fuel all over the fuse panel.

Replacing all of the fuel lines is a project that is definitely on the agenda.