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MG MGB Technical - Pertronix Ignitor Ignition Problem & Fuel Pump

Happy Labor Day Weekend!

Ok, I need everyone’s help again. Just to refresh everyone, my car is a basically stock 1973 MGB.

I have been working on cars for over thirty cars and have restored several cars from the ground up. So, I know a little about what I am doing - I think!!

Pursuant to my other thread called pertronix Ignitor Ignition, I installed the unit today. It was just like everyone said and it was very easy to install and I did it EXACTLY like the instructions said to do it. I double checked every connection. However, when I tried to start the car, it would not start. I only tried to start it twice. When I went to look to see what was wrong, the wires and the Pertronix unit was smoking and burning hot. I jerked the wires off the coil - and yes, the red wire was on the positive side and the black wire on the negative side of the coil - and they were not pinched any where.

When I started inspecting everything, I realized it had also melted the white wire running from the other positive connection on the coil. This wire runs up to the fuse box and then splits and goes on to the fuel pump.

So, I reinstalled the points but the car would not start - it ran this morning before I started all of this. Then I realized the fuel pump is now NOT clicking when I turn on the key. I checked and it has power at the fuel pump, so I can only assume that the Pertronix unit also has burned up my fuel pump. I am not a happy camper at the moment.

The question of the day is - This is a fairly new fuel pump - less then three years old (3,000 miles). Do I just replace it or try to rebuild it? Are the fuel pumps able to be rebuilt? Can I buy just the power side of the pump or do I have to buy the whole thing? Is it sold as a unit or can I pump the parts separately? Do you think the pump is burned out? What do you think is wrong with the pump?

Suggestions? Comments? Do you think Pertronix will pay for a new fuel pump for me????? Fat chance?

Thanks,

Robert
Robert Browning

Also, if you read the archives, there are a number of cases where people have had brand new Pertronix units that were bad.
Robert Browning

Several months ago, had exactly the same problem as you describe - new Pertronix Ignitor was bad out of the box. On switching on ignition, fuel pump did not tick and red wire from Ignitor to coil and white wire from coil (+) terminal to fuse box both melted. SU electronic fuel pump remained OK after incident.
willie L

Robert,
Sorry to hear this - I have heard it said that if the Pertronix is going to fail it will likely be out of the box or very shortly thereafter. Never had one go myself.

No way the Pertronix would fry the pump - you will undoubtedly find that you have no or reduced power to the pump, because the white wire circuit is toast. (Disconnect the pump wire and run a jumper from Battery+ to the pump to verify) This includes all the whites from Ign switch to fusebox, all connectors in the same stretch, and possibly the brown feed to the switch and the switch itself. Check voltage to ground at the switch, each connector, coil, and pump with analog voltmeter. Melted wires are usually obvious, heated connectors will give poor connections with no visual sign. Replace the connector sleeves.

For everyone's ease of thought, let me suggest that in discussing electrical circuits we all use the standard designations that the electricity, and therefore the wires, are going FROM the battery TO the load. Otherwise it gets difficult for everyone to follow circuits and sort trouble. The browN wire comes FROM the battery cable/solenoid, TO the switch. The White wire comes FROM the switch, TO several connectors (one of which feeds the pump), TO the fuse box, TO the coil.

FRM
FR Millmore

Robert - I agree with Fletcher, the petronix should not have caused any damage to your pump, but in melting the insulation of the white wire to the pump, you may have a high resistance in that wire now that cause an excessive voltage drop at teh pump. You should also check the ground for the pump, if you have voltage at the pump, but no ground (or a ground with a high resistance), the pump won't run. Jumpering the battery directly to the pump and insuring that you have a good ground to the pump should cause the pump to run. If it doesn't, then your pump is suspect. One question, you say you have been working onthe car for a long period of time, how long has it been since the pump was powered up and run? If the pump has sat idle for a year or more, then the points are probably filmed over, which will keep it from running. A good cleaning of the points with some 400 grit sandpaper should get you going again. If this is not the case, then e-mail me directly, regarding repair/restoration of the pump. Good luck - Dave
David DuBois

David,

Yes, I have been working on the car for several years, but the car has been drive able and has been driven on a regular basis. The car was running fine yesterday morning before I started the Pertronix installation.

Late last night I just checked the OHM resistance in the wiring to the pump and it was fine. Now, the pump “sometimes” will make one small click, but will not operate. I will run a direct line to the pump later this afternoon and check it.

Therefore, this goes back to my original questions. If it is the pump, is it repairable or do I replace it?

Thanks,

Robert
Robert Browning

Robert,
Checking resistance is not a valid test. You could, for instance, have a single strand of wire conducting, and it will show near zero ohms. Under load, you will have a massive voltage drop, because you are pulling current (about 5 amps by Dave's figures), which the ohmmeter is not doing. This will not provide sufficient power to operate the pump. Check voltage at the pump with the pump connected; it should be very near battery voltage.
FRM
FR Millmore

Robert. I would go further than Fletcher and suggest that you begin by checking the voltage at the white wire input (front, third fuse from the top) from the ignition relay. I have seen, once, a similar problem to yours and the wires had insulation melted all the way back to the ignition switch--including the brown wire which feeds the switch. You need to make a series of voltage checks and see if there is a voltage drop and, if so, find out why.

Les
Les Bengtson

Hi folks. I have a new Pertronix unit for my mga that I've installed in an original, rebuilt distributor. Is there a way to check out the Pertronix before I install the dizzie in the car?

BTW, I have trouble changing light bulbs so any advice appreciated!

Thanks,
Tom
Tom Custer

So where am I now?

First, I want to thank FRM, Les. David everyone else for their help, support and suggestions.

Second, I want to clarify something I wrote last night. I know that I needed to check the voltage in the wires. The reason I said I had checked the OHM’s was that it was very late, I was frustrated and my OHM meter was laying there, so I decided to use it.

Everyone has heard of Murphy’s Laws. Well, have you heard the one about how a $500 television picture tube will blow to protect a ten cent fuse? Thank goodness for me, Murphy must have take the Labor Day Weekend off.

As it turns out, the wire running from the coil up to the fuse box took the full blunt of the Pertronix short. It seems that this wire burned in half before the voltage could get to the rest of the wiring. When I checked the OHM’s last night, it indicated current. When I checked voltage this morning it was running about 6 volts. Then I touched the wire and the voltage disappeared. When I wiggled the wire it indicated an internal short. When I checked the voltage between the two white connections at the fuse box (third fuse down) and the fuel pump, it was about 13+ volts. The same was true for the wiring connections at the ignition switch. So this is why my fuel pump suddenly quit last night.

I spent this afternoon replacing the wire between coil and the fuse box.

Where I am now? I am back to exactly where I started off yesterday morning. I reinstalled the points and reset the timing and my car runs fine. I now have to contact Pertronix on Tuesday and start this all over again.

I would have to say that so far I am NOT impressed with the Pertronix products.

Thanks again for everyone’s help. I will let you know what happens when I get a new Pertronix unit.

As for Tom’s question, I would also like to know the answer. When I get the new Pertronix unit, how do I test it and protect myself from this happening again?

Happy Labor Day.

Robert
Robert Browning

Also, has anyone ever installed a in-line fuse between the fuse box and the fuel pump? Would there be any benefit? Any harm?

Robert
Robert Browning

Robert - Even though I have never installed a fuse in the line to the fuel pump (the cobbler's kids never have shoes), it is probably a good idea in that the line to the fuel pump is along run and could develop a short anywhere along the way. A fuse in that line would protect not only the wire to the fuel pump, but also the other wires in the same harness with the one to the pump. Cheers - Dave
David DuBois

Robert,
Well, congrats on finding your trouble.
I am a fan of fusing EVERYTHING. Fuses belong in all circuits, as close to the beginning (battery end) of the circuit as possible. ANY minor problem, like a wire rubbing on a sharp edge, can cause a fire that destroys the harness if not the car. People are likely to jump on me here, but I see no reason to not fuse the ignition circuit along with everything else. The argument is that "if the fuse blows, the car will stop in bad circumstances - on the freeway, in the dark, etc." But as you see, if the ignition unit (or anything else on the circuit) fails short, the car will stop AND burn down. All that can be said for that is that the fire department can follow the flames and smoke. Certainly put a fuse in the wire to the pump, that wire is very subject to damage on its trip rearward. Put a fairly large (35A)fuse in the brown feed to the IGN switch, and smaller ones at the split points for the pump and coil. While you are about it, fuse the feed to the headlamp circuit.
Ask Pertronix when you call "What is the maximum current draw?". It should be the maximum draw of your coil, plus a little bit, total about 4 amps for a standard MGB coil. About double that for a coil circuit protection fuse, say 10A.
This is how you test it too - put a 10A fuse in the white feed and hook it up, if it's bad the fuse will blow.
Also ask them "Is there any condition where the system has current flowing through the coil with the engine NOT running but key on?" I have heard that it is possible, but that is contrary to my understanding of how the thing is triggered.

NOTE that Lucas fuses are rated and marked for MAXIMUM current, but are rated at half the marking for continuous load, so a 35A fuse is good for 17.5A continuous. American fuses are marked at max ratings, modified by designations like slow or quick blow.
FRM
FR Millmore

Follow-up

I contacted Pertronix and they said that if the unit smokes like mine did, then it is probably a bad unit - stunning evaluation don't you think!!

I have sent the unit back and they are sending a new one.

As for FRM's question, Pertronix said that the maximum draw for this unit is less then one volt. I asked if there was any way to test the unit before it is installed so it does not melt my wiring again and they said, "not really". So the idea of a fuse in line as FRM suggest is the best idea.

I will keep everyone informed and let you know what happens when I get the new unit.

Cheers,

Robert
Robert Browning

This thread was discussed between 04/09/2005 and 08/09/2005

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