Fuel RPM Relay Not Engaging

[DeLoreanDMC81]

Hey everyone! So I clear up one problem and another pops up.

My problem this time is that my fuel RPM relay doesn't want to click on, to activate the fuel pump. I've been living in Utah for several months, them came home the other day to the car not wanting to start, from lack of fuel. My fuel pump works, I tried the relay jumper trick and the fuel pump runs, I can start my car and run it just fine using that trick.

I put an ohms meter on the rear pulse coil, I'm getting around 575 ohms, so at least I know it's getting power. I messed with it a little while ago, everything worked for about 20 seconds, then it died again. I have no idea what happened, or why it worked for that brief moment?

I did take the plastic cover off the RPM relay and touched the 2 connectors together manually, and everything works just fine.

So I'm at a loss, and have no clue what is going on?

Any help is greatly appreciated.

Thanks a ton!

James

[Michael]

http://dm-eng.weebly.com/

Get a RPM relay from Dave. I have several of his components in my car, excellent stuff.

The OE RPM relays run very hot and can cause problems with the soilder joints.

If you are on a tight budget, you might try reheating/resecuring the joints with a soilder iron but for 50 bucks I would just replace it if you have determined it to be faulty.

[DeLoreanDMC81]

Thanks for the info, his relay looks good.

My thing sadly, I just bought a new RPM relay from John Hervey and his is doing the same thing mine is doing. So I'm not sure what the deal is?

James
6408

[Michael]

Once again you will have to make sure you are getting enough power to the RPM relay using your mulitmeter. You said in your last post on the headlights that pulling replacing the fuse fixed it. What you probably did was scrape a little corrosion off the blade and gave it a fresh clean contact point. Did you clean all the fuses? Do that, then clean all the grounds. Dirty fuses and bad grounds can cause all kinds of problems that you will chase until the end of time.

[Bitsyncmaster]

Some of the RPM relay do not prime the pump when you turn the key on. So if that's your test, try starting anyway. Many of the OEM RPM relays get bad solder joints that make it intermittent. Those broken joints are caused by the heating of the unit made with a single sided circuit board. Some OEM units will prime with the key in some cars. Basically the unit sees a pulse on the ignition when the key turns on and that causes the one second prime.

My solid state RPM relay runs via a microprocessor. So it will always prime in any car because that is a function of the software. My unit is made with a double sided circuit board and does not heat up like the OEM unit.

I do recommend replacing the fuse block with DMCs replacement block. The OEM fuse block pins were very poor for making good contact onto the fuses. The new replacement pins are very good. It's a lot of work to replace the block but should fix a lot of electrical problems.

[Jonathan]

Thanks for the info, his relay looks good.

My thing sadly, I just bought a new RPM relay from John Hervey and his is doing the same thing mine is doing. So I'm not sure what the deal is?

James
6408

A couple other ideas of things you could check:

- Could be a wonky connection at the inertia switch, or the switch itself intermittently cutting out the fuel pump.

- If you have an automatic and the problem is more just starting the car initially, the gear shifter needs to be all the way up into Park to satisfy some interlock switch that is tied into the ignition circuit. If it is not quite up all the way, you can't start the car.

[sdg3205]

If jumping the relay harness runs the pump then the inertia switch should be fine. Verify you have the white dot inertia switch recall mounted to the body, not the lambda counter bracket. This will save you more headaches later. Factory inertia switches always failed and killed the pump.

On that note, has there been any wiring tampering? It is extremely common to see POs wire the inertia switch OUT of the picture instead of replacing it. Make sure you're stock before proceeding. PO rewiring jobs are not better.

If you can manually engage the rpm relay with your finger with the cover off, the relay is probably toast.

Then buy daves solid state rpm relay and never worry about the relay again.

[chris williams]

My thing sadly, I just bought a new RPM relay from John Hervey and his is doing the same thing mine is doing. So I'm not sure what the deal is?
I had two that were bad and he replaced with good ones, so probably one of these.
Chris

[DeLoreanDMC81]

I've been the owner of my car now for several years, the guy I bought it from didn't know much. So I'm betting not much wiring tampering has been done. lol

Now I've been out in the car for quite a while now, cleaning up connectors and things, but it hasn't made an difference. I checked the inertia switch and it works like it should.

I went ahead and inquired about Dave's solid state relay, so I'm going to pick one of those up.

Here's another question, when you turn the key to the "ON" position, is the Lambda relay suppose to click on? I took the cover off my old one and the only time it clicks over, by itself, is when I manually touch the connectors on the RPM relay together with my fingers. I'm just trying to rule out the possibility of a defective Lambda relay.

Thank

James
6408

[Bitsyncmaster]

I've been the owner of my car now for several years, the guy I bought it from didn't know much. So I'm betting not much wiring tampering has been done. lol

Now I've been out in the car for quite a while now, cleaning up connectors and things, but it hasn't made an difference. I checked the inertia switch and it works like it should.

I went ahead and inquired about Dave's solid state relay, so I'm going to pick one of those up.

Here's another question, when you turn the key to the "ON" position, is the Lambda relay suppose to click on? I took the cover off my old one and the only time it clicks over, by itself, is when I manually touch the connectors on the RPM relay together with my fingers. I'm just trying to rule out the possibility of a defective Lambda relay.

Thank

James
6408

With the stock RPM relay, if it primes it would also run the lambda relay for the same prime time. With my solid state relay, the prime only runs the fuel pump.