MFI help required: cold start & microswitch

[2.4te]

Please could those of you in the know with MFI walk me through diagnosing two issues? My car is a US spec 1972 2.4 TE with MFI. In fact I bought it when I lived in San Francisco and shipped it home to the UK when I relocated back there. This year is my 10th year of ownership and I do most of the work on it myself.

I have CMA and my engine runs well, but I’m sure the cold start system is not working and also, neither does the microswitch seem to operate (when I perform the CMA test of running the engine to 2000rpm and depress the microswitch, nothing happens). I’m pretty mechanically adept, but need an ‘idiot’s guide’ to diagnosing electrical problems, which I presume is the cause of both problems. I have a voltmeter, but need someone to tell me which wires to test and how, which is why I haven’t got on very well with CMA alone and reading through previous posts on this subject here.

Many thanks.

Dr Dave

(Birmingham, UK)

[210bhp]

Dr Dave

Check out this thread on DDK where I had a very similar problem and solved it with help from the other guys.
If you need more info send me a pm

http://www.ddk-online.com/phpBB2/viewtopic.php?t=14994

Regards
Mike

[304065]

Dave, search here with user name Early_S_Man and "Speed Switch" and you will uncover about 20 threads discussing every aspect of the system, all the way to a schematic for the board inside the switch. This is one of the most thoroughly covered items of the MFI system.

Good luck!

[Grady Clay]

Dr. Dave,
First, WELCOME to the Forum
You will find a lot of help here.

There are (at least) two separate issues here.

The microswitch, RPM sensor and ‘shut-off’ solenoid work in conjunction to turn off the fuel during deceleration. The basic criteria are (1) Off throttle (microswitch), (2) rpm above 1500 and (3) ignore throttle position. The functioning of this system is ‘down the list’ compared to most MFI issues.

Next is the issue of cold start and cold running. There are distinct differences between the two but they are interrelated. One issue is MFI tends to run best when set too rich. This tends to mask some starting and cold-running issues. Aside from the basics (cold start and cold run thermostat), I would concentrate on the normal running first.

Perhaps an exhaust gas analyzer and a data-taking passenger would be useful as a first step. This will tell your basic running mixture. You will want to know it at idle, part-load and full throttle at various rpm. I suspect you will find it “too rich”. Once you get the main running correct you can then address the other issues (rpm overrun and cold start).

This forum has an unbelievable resource of MFI experts to help you through this process. Welcome again.

Best,
Grady

[FenderBender]

Dr. Dave,

Welcome, you came to the right place. I would have been lost with out these guys and this board.

First listen to these guys, I know it is a P.I.A. But the CMA is the way to do it.

I just fixed my RPM Transducer with the help of this board. First I checked my microswitch with a continuity test on my voltage tester. When the switch is closed you will hear a beep, when open no beep. My switch was working.

I then removed the RPM Transducer and found 3 capaciters with broken legs. One had two broken legs. I resoldered them and hot glued them along the tops to help stabilize them. Works great now.

Check out this thread. WARNING - All '69-on MFI Owners!!! Preventable Failure of $283 Speed Switch module!

Also do a search on the ultimate mfi thread.

Good luck,
Mike

[2.4te]

Guys, thanks so much for your input and warm welcome. I’ve lurked here for several years but never posted. I even have printed off many past threads for my (2 inch thick) MFI compendium, as I once recall Grady suggesting. In fact, I have a copy of that very DDK thread Mike, thanks very much. The thing is, I’m easily intimidated by automotive electrics, I guess because I don’t understand them. For example, in the DDK thread on the microswitch issue, Mike says ‘Yes, I can operate the solenoid externally and the engine dies like it should when 12 volts are applied.’ But how do you operate the solenoid externally and how do you apply 12volts. Mike FenderBender says to do a continuity test on a voltage tester, but again, I need to be told how to do this. This is what I meant by needing an idiot’s guide!

Grady hit the nail right on the head with my car’s problem. Let me take a moment to describe the history, forgive my indulgence but I think it might help diagnosing the problems: When I bought the car it had the numbers matching engine. Even though I had a PPI that gave me the green light to purchase, it wasn’t long before I doubted the integrity of that PPI and realised the engine was a little tired. The valve guides were shot at very least. A few years later, and back in the UK, it became time to do something about the engine. I should say it started perfectly etc, no cold start issues, though perhaps even then it was running rich; it just smoked terribly, especially on the over-run.

An opportunity then arose to buy a ‘rebuilt engine’ from a ‘respected specialist’ in the UK. This was when I got stung. I decided to take this route, buying the engine that came ready to bolt in including SSI heat exchangers, because the cost involved was defined, not the case when rebuilding an engine. In fact I installed the engine myself because I wanted to and because I wanted to powder-coat the tinware, paint the engine bay to tidy it up and have the gearbox checked over. However, the engine ran very badly when I got the car back together, but the ‘respected specialist’ wasn’t interested. After getting totally despondent and almost selling the car over the next couple of years having spent so much on it, I bumped into Dominic Toni here and on DDK, who’d had MFI problems. He inspired me to sort out the problem with my car and eventually (winter of 2006) I decided to switch MFI pumps from my original engine, which I’d kept in the garage to rebuild one rainy summer when my boys are old enough to help and learn.

What a result! Immediately the car was 100x better. It started fine and ran well, but still wasn’t quite right. So, late last Spring when the weather was warmer, I took it to a genuine expert, Bob Watson in the UK, who set the car up on his rolling road. It was indeed running rich as Grady suggested and Bob sorted it so that it now made 141bhp, and the factory figure is 140; Bob commented on how flat the torque was and how well it drove.

I drove home very happy- it ran beautifully, the best my car has ever run. Until the next morning. When I couldn’t get it to start without cranking endlessly! I ended up taking 3 washers out of the warm-up thermostat and it started, just. Through the summer, starting was difficult, but I lived with it, even talking it to Le Mans. Now, early Spring, I’ve dusted it off after winter hibernation and it’s almost impossible to start. I’m sure the ambient temperature is lower than at any point last year when I was using it after the rolling road session and that must be exposing my lack of cold start. So here I am!

Grady, do I need to get an exhaust gas analyzer, or can we rely on Bob Watson’s rolling road session (given that I can re-fit the 3 washers to the warm-up thermostat I since removed) and begin to get the cold start system working?

With kind regards,

Dave

[2.4te]

I've been having a look at my car today. I disconnected the wire (brown and grey striped) that runs to the terminal of the cold start solenoid on top of the fuel filter console. I connected a bulb between the wire and its terminal on the solenoid. When I cranked the engine, the bulb did not come on. I then connected my bulb between a live supply and the cold start solenoid terminal. The bulb lit up, but there was no sound from the solenoid. Am I correct in thinking (1) I don't have power getting to the solenoid and (2) the solenoid isn't functioning? How do I trace the problem with the power supply to the solenoid?

[Flieger]

Sounds like it is too lean now at low speed/cold temperature. Maybe you could richen the idle screw on the injection pump? This is relatively simple as long as you keep very careful track of any adjustments you make.

Remember: I Lean Left- Turn idle screw left(anti-clockwise) to lean the mixture

[Flieger]

Oh, and if this screws the running up even more, use your notes to put it back where it was, of course.

[Peterfrans]

The cold start circuit consist of the following parts:
A black standard relay on the relay plate in the engine bay
A thermo time switch on the breather cover on the crankcase
A solenoid on top of the fuel filter.

The cold start circuit works as follows: When cranking, current is supplied to a thermo time switch. Depending on engine temp this switch will ground the black/red wire that goes to terminal 85 of the black relay for a finite amount of time. As long as this wire is grounded the relay will power the solenoid on top of the fuel filter and fuel will be squirted directly into the intake stacks.

I would start by checking fuse no2 in on the engine bay relay plate. This fuse feeds both the cold start relay and the speed switch. Make sure that both terminals are clean and that the fuse is intact.

If you have current here, it is time to check the other components.

Pull the black relay. On the botom of this relay are the numbers corresponding to the function of the respective terminal.

1. with the key in engine run position check if 12 volt is available at terminal 30.

2. to check the solenoid, pull the full hose from the solenoid and replace it with a length of hose ending in a suitable container. Take care because if the solenoid works, raw fuel will be pumped out rapidly. Now connect a 12 volt source to terminal 87 of the relay (key still in the run position to power the fuel pump). If the solenoid works fuel will be pumped into your container. If not, either the solonoid or the wiring to the solenoid is broken.

3 to check the thermo time switch, pull both wires from it. Connect the terminal where the black/red wire was to a test lamp, connect the other side of the test lamp to +12v. Now connect the other terminal (where the yelow wire was) also to +12 v. If the switch works, it should ground the testlamp for a small amount of time, the light will be lit for a few seconds and then go out. If this is not the case replace the switch.

4 check if the black relay is powered during cranking. 12 v should be available when cranking at terminal 86 of the black relay.


If the solenoid and the thermo time switch are ok, and 12v is availble at the right terminals of the black relay, replace it with a known good relay (for example the horn relay from fuse box in the trunk). See if it works now.

As your speed relais also seem to be inoperative, my bet is that there is something wrong with the fuse.

BTW, I would replace the discs in your warm up thermostat. If the car has been set up by Watson, removing these will also influence the mixture when the car is warm.

[2.4te]

Thanks fo the replies. Peter, you mention "A black standard relay on the relay plate in the engine bay". Please could you identify it in the figure, which I obtained from 210bhp Mike's post on DDK. I've identified all the other components and have cleaned the thermo-time switch connections, but have yet to test it. I can confirm fuse no. 2 is ok (item 10 in the figure).

[Peterfrans]

thats number 4. Number 2 is for a single stage heated rear window, which is not installed on cars equiped with a two stage heated screen

[2.4te]

Thank you Peter. I'll work through your suggestions tomorrow.

[2.4te]

Today, I spent my time cleaning terminals and then I ran the tests Peter suggested. IMy results follow:

I would start by checking fuse no2 in on the engine bay relay plate. This fuse feeds both the cold start relay and the speed switch. Make sure that both terminals are clean and that the fuse is intact. Yes

If you have current here, it is time to check the other components. Yes

Pull the black relay. On the botom of this relay are the numbers corresponding to the function of the respective terminal.

1. with the key in engine run position check if 12 volt is available at terminal 30. Yes

2. to check the solenoid, pull the full hose from the solenoid and replace it with a length of hose ending in a suitable container. Take care because if the solenoid works, raw fuel will be pumped out rapidly. Now connect a 12 volt source to terminal 87 of the relay (key still in the run position to power the fuel pump). If the solenoid works fuel will be pumped into your container. Yes, fuel .

3 to check the thermo time switch, pull both wires from it. Connect the terminal where the black/red wire was to a test lamp, connect the other side of the test lamp to +12v. Now connect the other terminal (where the yelow wire was) also to +12 v. If the switch works, it should ground the testlamp for a small amount of time, the light will be lit for a few seconds and then go out. Yes.

4 check if the black relay is powered during cranking. 12 v should be available when cranking at terminal 86 of the black relay. 10.6v obtained, not 12v. Is this the problem?


If the solenoid and the thermo time switch are ok, and 12v is availble at the right terminals of the black relay, replace it with a known good relay (for example the horn relay from fuse box in the trunk). See if it works now. No.

BTW, I would replace the discs in your warm up thermostat. If the car has been set up by Watson, removing these will also influence the mixture when the car is warm. Replaced!

I found that if I connected a 12v supply to the solenoid it activated and pumped fuel. However, if there was a bulb in that supply wire, the solenoid did not activate. I don’t know why that would be.

So, I’m not sure where to go next, if you could help I would appreciate it.

[2.4te]

I meant to say, all the tests were performed with the speed switch removed (no. 5 on the diagram in this thread), since when I removed the relay plate to clean everything today, I could hear a rattle, which turned out to be dettached components inside the speed switch. I opened it up and inside looks very unhealthy- 36 years of corrosion. Are these units still available? Clearly, my unit is non-functional.

[Peterfrans]

Nice to know that basically the cold start system seems to work. However, 10.6 volts might be to low to power the relay. Is your battery ok?

I don't think the speed relay is still available. I would post a wtb in the for sale and wanted section of the board.

[2.4te]

Yes, batteries are ~perfect

[304065]

Dave, speed switches are available as rebuilt units, try Ottos Venice (if Pelican can't offer them, which I don't believe they do.

Put the washers BACK in the thermostat! Removing them just makes the thing run unbelievably rich all the time-- e.g. the circlip on the rod is on the outside of the washers, as shown here:
MFI thermostat spacers

A salacious way of remembering this is "WHEN YOUR ROD GETS HOT IT GETS LONGER" and removing the discs will keep the mixture perpetually around 10:1, resulting in Very Bad Things happening.

You are going down the right track, speed switch has nothing to do with cold starting, so if the car won't start fix the cold-start circuit. The speed switch may result in better fuel mileage or fewer backfires in the exhaust, although many, many pelicans run without them (mine's been INOP for five race seasons).

Good luck!

[domtoni]

Dave,

This is what my car ran at some time back. Chris set it up to run this way based on exhaust gas analyzer. I think the car is running pretty clean now that Bob set up the recalibrated pump.

Unsure if the surging is MFI or Distributor related

Best
Dom

[FenderBender]

Dave,

I found this member rebuilds them. http://forums.pelicanparts.com/members/1511.html

There was someone selling rebuilt ones for $75.00 but I can not find the post It was in.

Good Luck, Mike