What is the proper size of the fuse for the fuel pump, the one on the relay board? If your blowing that fuse does it mean the pump is going or gone?

Ian Stott
Moncton
Canada

My test ride was going great til I got abot 500 meters from my house!

Could be your AAR is shorting out, and causing the fuze to blow. Unplug the AAR and see if the problem persists.

Ian,
Just sent you a PM on the relay board. The fuse for the fuel pump is the rear one on the relay board. I run an 8 amp. Normally there is a 25 amp there, but I do not have the rear window defrost or my heater fan hooked up. 8 amps works fine for me. What size fuse did you have in it when it blew? If it was the 25 amp, I'd be looking for why it blew! How far back in the wiring harness did the damage from the fire go? Just wondering if you got all of the problems repaired.
Tom

I went for my test drive which lasted for more than an hour, three different stops, one to drop my idle down which was at 1300/1350 where before it was at 950/1000, engine really smooth at any RPM, new points, rotor, and cap, really pleased with the way the engine was running (cause I want to go to Owl's Head in Oct.) Coming down the ramp off the TCH to go home it died, fuel pump fuse on the relay board blown, a blue one and brand new, replaced it with a new blue one, blew that immediately, wife towed me home, about 500 meters and lots of people watching! My mechanic thinks I need a new fuel pump but we were only talking on the phone, he hasn't looked at it yet.

Ian Stott
Moncton
Canada

Isn't the blower motor for the heater on the same fuse?

Yes the blower ( fan ) motor is on that fuse also. In my post I indicated mine is not hooked up. I only have for loads the fuel pump and AAR.
Ian,
If it imediately blew a 25 amp fuse, Try this: With the key off, disconnect the 12 pin connector ( right rear of relay board ) and measure pin 12 to ground. Should be a white wire. Also should be about 13 ohms + or minus an ohm or two. If it is way less, leave the meter hooked up and wiggle the AAR wire at the AAR to see if the reading changes. Usually the insulation wears at the point of entry into the AAR.
Tom

Thanks Tom, We will do that,and just a note re. the blower on the same fuse, it wasn't on, nice day here today. Hmmm does the AAR have anything to do with idle speed?

Ian

AAR regulates the idle when cold and working properly. As it warms up, it shuts off the air flow. Sounds like you may have something going on with it. If it started shorting, it would take power from the AAR and it would cool off, opening the air circuit to increase idle speed.
Check that 0.5 mm white wire for heat damage in your ignition harness. Hopefully it shorted enough to blow the fuse before damaging the wire. That white wire is only rated for about 10 amps. Protecting it with a 25 amp fuse is not smart engineering!
Tom

Well,well, I had a short in the wire that goes under the air intake, it had rubbed itself bare, a few inches of well placed electrical tape and I am running fine. Heading to Owl's Head Maine on Friday, hoping to take a ride in WW 1 vintage Biplane and also enjoy a great car show.

Ian Stott
Moncton
Canada

Hey Ian,

I had an AAR go semi-bad on me on Sunday (not closing all the way), and it apparently took the relay out. Suddenly, the last relay was dead, the fuel pump would not ramp up and I was pissed. I unplugged the AAR, put in a new relay (tested it with the hot air fan) and drove home. The car started on the first try with the working relay.

You were fortunate. I bought a replacement AAR today.

So it goes with 39 year old cars.

Glad you are running again. My first AAR actually was shorted out and blew by my hand touching it to ground. POW. Sparks and all.

Forgot to disconnect the battery when messing with the AAR lead.

John

I don't really have a fast idle when cold, it runs a little rough but smooths out nicely when warmed up, is the AAR the culprit here?

Ian Stott
Moncton
Canada

Ian,
Sounds like your AAR may be stuck. A lot of that going around. You can check for proper operation by removing the line from the AAR to the air cleaner and putting your finger over it. Do this just after start up. If the idle goes down, your AAR is open. A few minutes later after the engine is warmed up, do the same test. Putting your finger over the line should make no change and you should feel no vacuum on it.
Replace that taped wire soon!! At rhe very least, heat shrink it. Electrical tape when heated tends to let go.
Tom

Ian, I don't know if you've ever sat in the front seat of an open cockpit plane but imagine trying to look into an 80 mph fan 36" in front of your face. You need to bring some goggles (or large pair of safety glasses at min) if they aren't provided for you. Sun glasses and eye glasses help some but don't turn your head or they'll blow right off. Have fun!!!

I experienced a similar issue with a more dramatic consequence. If the wire grounds out again there's no guarantee the 25A fuse will protect the ignition harness from meltdown -- an expensive and messy problem. Afterwards, and since I wanted to keep the power going to my blower, I did as Tom suggested and installed a simple in-line fuse for the AAR. It required no more time than just splicing a new wire.

Since your also having an idle issue you may as well R&R the AAR or it will continue to fight you. Some suggest bypassing, but you may like having it up there in N.B.

Here's to your making the show.