Rapid clicking from the RPM relay on hot start

[Kenny_Z]

After a warm up the RPM relay is clicking rapidly on cranking. I stopped by my parents house and only spent about 20 minutes there to get to this condition. This relay is less than 2 weeks old. I thought it was my fuel accumulator telling me I had to stop putting it off and replace it.

When I first installed the relay in the car she bucked a lot during acceleration. I pulled into a parking lot and let her idle while I checked all the connections. I didn't shut the engine off while doing this. The idle was fine so I pulled back on the road and had no more weird bucking for the rest of the half hour test drive.

Today I finally swapped out my fuel accumulator and pressure valve orings but I'm still getting that rapid clicking from the RPM relay and it takes a long time to start when hot. I swapped in my old relay and she fired right up. It did do that horrible bucking again with the old relay installed but this time it didn't go away when I poked around in a parking lot, I installed the other relay after shutting down the engine and then it fired right up. I guess the new one had time to cool down. No more bucking on the rest of the test drive. When I got home I parked her since I was frustrated and spent the rest of the day on another car.

Tomorrow I'm going to install the original relay and go for a long drive. Then I'll bring her back to the house, give it about 20 minutes and try to crank her. If I get that rapid clicking from the old relay (which has never done that) I guess I'll be looking into the other relays I replaced.

[Bitsyncmaster]

The RPM relay just looks for ignition pulses to keep the fuel pump running. If your getting clicking during startarting then my guess would be your battery or one of the major battery connections is bad. If your seeing normal battery voltage with the engine running and are still getting an intermitant RPM relay then it points to a bad connection and not a bad battery.

This all assumes one of your RPM relays are good.

[Kenny_Z]

Thanks for the input Bit. I didn't get to do my drive today since my parent's needed help. I got home and inspected some cables. The positive leads between the bulkhead, alternator, and starter look suspect to me. I'd like to replace them. Would a pair of 4 gauge cables work? Or should I bite the bullet and order from a Delorean vendor?

[Bitsyncmaster]

Thanks for the input Bit. I didn't get to do my drive today since my parent's needed help. I got home and inspected some cables. The positive leads between the bulkhead, alternator, and starter look suspect to me. I'd like to replace them. Would a pair of 4 gauge cables work? Or should I bite the bullet and order from a Delorean vendor?

You would probably be OK with one 4 AWG. But larger wire will give you faster cranking for cold weather starts.

4 AWG = 41,740 cir/mil
2 AWG = 66,369 cir/mil

So two 4 AWG wires have less voltage drop then one 2 AWG.

[Kenny_Z]

Thanks Bit, I'll do that swap soon.

So I did my test drive this morning by taking the D to work (old relay). She drove great. I got to work, set the timer on my phone for 20 minutes, and then went to work. At 20 minutes I went back to the car and she wouldn't fire. I could get her to turn over but it was like there was no spark. I swapped in the new relay, no luck. I jumpered the relay connector and let the fuel pump prime. She still wouldn't fire and I smelled a lot of fuel so I think I flooded the engine.

I crawled around the car checking all the main electrical connections. The back of the alternator was tight but I was able to get a slight turn on the connection to the starter. She still didn't start. I don't have a coil cover, there wasn't one on the car. As a result the coil is hot. Other than that I have no idea what is going on. She will not start until she's cooled down.

I just walked out with one of my coworkers, I pulled a plug and he watched for spark while I tried to crank it. No spark at all.

[Bitsyncmaster]

No starting after a 20 min. wait is a sign of a bad fuel accumulator but I'm not sure if that would be a problem in the cooler weather now.

If it starts find after a four hour wait then you should check that fuel accumulator.

[Kenny_Z]

I just swapped the fuel accumulator this weekend along with the pressure valve orings. This particular hot start problem existed before the swap. Plus, this is a no spark problem for sure. Unfortunately I did not bring a spare ignition cable with me to test for spark before the distributor.

[Kenny_Z]

It was the coil. That coil is less than 3 months old but it must of died. When I pulled ignition wire 1 and tested right off the old coil I had no spark. I bought and installed a coil from NAPA and she fired right up.

[Totally 80s]

Was the 3 month old bad coil made in China or some other slave labor country by any chance?

[Kenny_Z]

It was an accell coil but unfortunately I jumped the gun. While that new coil did get me home from work my hot start problem still exists. I was just disgusted with everything I went through with the car that I parked her for now. I'm going to need a short cool off period before I can deal with Red again.

The old relay does not click rapidly but I get no spark on hot starting.

[Kenny_Z]

Ok, finally ready to deal with her again. This morning I fired her up to find the new accumulator and pressure orings seem to be doing their job since she turned over twice before starting. Then I took her for a drive. She loves this cool weather I guess because she ran great. I got home and set my timer for 10 minutes. At exactly 10 minutes I went out and have the exact same problem.

I pulled the coil ignition wire and borrowed the wire from a spare set I have for my inline 6 Nova. Since I'm by myself here I hooked up a sparkplug to a jumper cable and put it where I could see it while attempting to start the car. I didn't see a spark with a spark plug straight off the coil. I'm going to have to do this test at night or wait for my neighbor to get home to be sure though.

I took some voltage readings with the key on:

Positive battery jump point: 12.12 (key off is 12.6)
Left side of resistor - 9.46
Right side upper - 11.5
Right side lower - 7.74
Coil positive - 7.57
Coil negative - 1.5
Ignition wire - 1.71

I also tested the spark plug with key on (keep in mind straight off the ignition cable on the coil) I was getting .9 volts.

I'm going to have to wait for her to cool off since I didn't take voltage readings before the drive for comparison.

[Bitsyncmaster]

Your ignition voltages look good. You need that neighbor to turn the starter for you.

[Kenny_Z]

Dad came over today to give me a hand. On start the positive side of the coil gets 8.33 volts and the negative is at 3.15. There is spark but it looks weak.

However, the source of the problem appears to be fuel related. I had to jump the CSV with the grey plug from the WUR and she started. Jumping the RPM relay doesn't help, I can only get her to crank by jumping the CSV. After doing this I can shut her down, swap the cables, and she'll crank properly. I've got new pressure orings and a new accumulator. This problem existed before they were swapped with one exception, I was able to crank the car after a few minutes of trying prior to the part replacements.

Any ideas?

[Bitsyncmaster]

Your really going to need to get a fuel pressure gauge unless you want to start replacing parts by guess. You may just have to adjust the mixture but not knowing if the primary pressure and control pressures are good you may just patch the problem.

By the way. When a car "cranks" it means the starter is turning the engine over even if you get no start or almost start. I assume you meant to say the car starts. I use the term "fires" if the car is almost starting because your hearing some cylinders igniting.

[Kenny_Z]

Looks like I get a new tool in the shop. I'll start shopping for a tester.

You're not the first person to tell me the correct terms. For some reason they just don't stick. I'll try to be less confusing in the future. Thanks for all the help.

[Kenny_Z]

I'm still waiting for my fuel pressure gauge to come in but I think I found a possible source of my pressure lost. I had the car up on ramps today to install some new rubber bushings in the shift points. I thought I felt moisture on the accumulator connections. After I got the bushings in I ran the car awhile to build up pressure. Sure enough I feel a bit of gas coming seeping through the threads. I wasn't able to tighten any of the connections under there and the only one that had moisture was the metal line. Is there any thread sealant that is safe for gasoline lines that I can use?

On a side note I did get the chance to grab some interesting voltage numbers. I installed Hervey's fuel filter/baffle kit today. Seems my original baffle didn't have the bottom plate. I felt around in the tank but I only found my missing filter, no baffle bottom. Anyway, I have a ground run straight to the fuel pump from the frame. I took this off and hooked up my voltage meter with some clamps. Here's what I recorded:

Turn key to on: 0.00 volts (I know I've seen posts asking if the pump turns on before the key is turned to start, mine does not)
Pump running without ground: between 10-10.5
Pump running with ground: 11.92 volts steady

A ground straight to the frame bypasses the inertia switch doesn't it? If so I may remove this ground and ground the inertia switch to see if I get any different voltages.

[Bitsyncmaster]

Threaded lines can use Teflon tape but I can't remember if all the lines on the accumulator are compression type seals.

[Kenny_Z]

I received my fuel pressure tester in the mail today. I hate this time change, it's too dark to do anything with the car when I get home from work. I really don't want to push the Nova out of the garage again this year. Last time it set my restoration project back 6 months. I'll have to wait until saturday to do anything unless I get brave enough to put some electric lights up.

I was wrong about the CSV starting this engine. Unplugged or plugged in it has no bearing on the engine starting when cold and jumping it after a 20 wait on a hot engine will not help the engine start. I'm going to run though a list of things just for my own sanity.

1 Pressure plate resistance feels the same at 20 minutes or 4 hours after a drive.

2 Accumulator and pressure valve orings were changed (issue existed prior to this except I was able to get the car to start after a few minutes of cranking and resting periods)

3 WUR jumped to CSV doesn't start a 20 minute sitting hot engine

4 At both 5 and 10 minute sitting periods on a hot engine the engine will start but struggle to stay running. Pumping the throttle does nothing to change this struggling tone. The struggling ends at about 30 seconds into the idling.

5 Fuel filter system changed from stock baffle and lines to Hervey's kit with no effect on hot start. (fuel pump not changed, not sure if this is an updated pump with external check valve)

So, my ever expanding to-do list:

1 Check check valve if possible
2 Teflon tape on fuel accumulator connections
3 Test fuel pressure
4 Test injector spray patterns
5 Check for leaking CSV
6 Compression check
7 Check and clean the plugs (They didn't look fouled last week)
8 Check for vacuum leaks when cold and then hot
9 Check timing

If at that point she isn't fixed I may get some concrete blocks and invite the neighbors over to see my new lawn ornament :dead:

[Kenny_Z]

I WON! I'm soaked to the bone, probably will be sick as a dog, but I beat Red. Tonight after a full warm up with a fuel pressure gauge on the car I shut her down and saw my pressure go from a nice ~70psi to zero. This time she wouldn't crank right after the shut off which she'd never done before. However, I was messing with the WUR connection hose right next to the pressure regulator yesterday while playing with the fuel pressure gauge. I pulled it out and found that the smallest oring had a huge nick in it. I'm guessing I either tore it on installation or it broke in the car. When I messed with the hoses I must of freed the piece that was helping block the 20 minutes of pressure.

Thankfully I don't throw anything away including my old oring. It wasn't damaged, I just replaced it because I was there replacing the larger one that was shredded. I put the old oring back in and reinstalled the regulator. It took some cranking to bring the pressure back up but she did start. I ran about 10 minutes before it started to drizzle then I shut her off and watched the pressure. I dropped to about 40psi within the first 2 minutes and then held at about 30psi until I just couldn't take the rain anymore.

It looks like my rest pressure is lower than it should be. I think the old oring is slightly deformed from age but at least it isn't nicked. Tomorrow I'm going to the auto parts store and buying about 20 of those orings.

[Bitsyncmaster]

That O-ring has caused so many starting problems.

Your rest pressure will imeadatly go to around 42 PSI when you shut the engine off. That is normal. If your in a hot weather state you want to hold rest pressure (above 5 PSI) for 4 hours or longer. At least that is what I found with my car. It drops to 5 PSI after 3 hours and if I try to start it at 3.5 hours it won't start (in the summer). After 4 hours the engine has cooled enought to start.