Possible Bad RPM Relay? Car starts but immediately dies after Coil swap.

[Beachdrifter]

Hi All,

So the last time I started my car with no issues was on Saturday.
Car started up just fine, as normal.

I spent the next 2 days recovering my seats, and also decided to replace the original Bosch ignition coil with a newer Bosch coil (# 00027). I did this as a preventative measure since I was tired of seeing a 30 y/o coil in the car and thought it was a good idea.

So today I go to start the car, it starts, but as soon as it hits idle RPM range, it sputters and dies. Initially I thought it was the new coil, so I went back to the old one.
I started it again a few times, and same.

1. I hear the Fuel pump Buzz as normal prior to start.
2. I've checked the #7 fuse, looks good.
3. When I manually jumped the RPM relay #30, 87 pins. I expect to hear the fuel pump run, but nothing happens. When I connect the relay back, and put the key to the "on" position, I hear the pump buzz/prime.
4. When I installed the coil, I ensured the terminals were connected properly.
5. Currently the original coil is back on the car.

I'm confused, prior to this the car was running perfect. Did I "fry" something by using the new coil; is it possible my RPM relay got "shocked" by the new coil through terminal #1? Is my RPM relay bad? I want to say it's almost like once the car starts, immediately the fuel is not being supplied and dies. It's like it's only getting the fuel from the initial prime of the pump right before I turn the key.

I doubt this has anything to do with cold start issues, since the car didn't have any prior to this. Thanks for any thoughts!

-Randy

[DeLorean03]

3. When I manually jumped the RPM relay #30, 87 pins. I expect to hear the fuel pump run, but nothing happens. When I connect the relay back, and put the key to the "on" position, I hear the pump buzz/prime.


This is your hint. When you jump those terminals, your fuel pump should turn on. For it to not be happening, it hints at something being on the fuel pump side of the circuit. Check the pigtail connector that hooks the car's wiring up to the fuel pump - make sure it is nice and clean. Double check your fuel pump's ground. I believe it is at the inertia switch - make sure the ground there is sound. Make sure the inertia switch somehow didn't get tripped and is keeping you from starting your car (doubt this is the problem).

If your car is starting and dying immediately, it is not a cold start issue - it is more than likely a fuel delivery issue. If the coil you installed is an identical blue one like the factory original with the same specs, you didn't damage anything.

I'm betting there's a bad connection at the fuel pump - either 12V or ground.

[Bitsyncmaster]

As stated, jumping the RPM should have made the pump run until the jumpers are removed. When your car starts OK then stops releasing the key it suggests your white wire on the resistor block (for the coil) has a bad connection.

Sounds like you have two problems. Fuel pump circuit and ignition circuit.

Ignition circuit could be a bulkhead connector fault. Try removing and plugging back in the bulkhead connectors.

[David T]

As stated, jumping the RPM should have made the pump run until the jumpers are removed. When your car starts OK then stops releasing the key it suggests your white wire on the resistor block (for the coil) has a bad connection.

Sounds like you have two problems. Fuel pump circuit and ignition circuit.

Ignition circuit could be a bulkhead connector fault. Try removing and plugging back in the bulkhead connectors.

There are a LOT of things that can go wrong and keep the fuel pump from running. If jumpering the RPM relay doesn't make it run other possibilities include:
Melted #7 fuse or a bad connector in the fuseblock
Bad connection at the pug up by the windscreen washer box
bad connections on fuel pump
bad fuel pump
bad inertia switch (MUST have a splotch of white paint on it)
creative wiring modifications by DPO's.

Once you can get the fuel pump to run consistently by jumpering the RPM relay and turning the ignition switch on, you can figure out if you have any other problems. If you are low on fuel and you have a bad pick-up hose, even if you get the pump running you may not be getting fuel to the motor. Pull the pump and inspect the hose. Even though the previous poster is suspecting a bad bulkhead connector, although it is possible, there are other, more common problems that should be investigated first.

[Beachdrifter]

Ok, so it turns out I got my fuel pump to run when I jumped the relay using 30, 87. All the fuel pump connections are good.

Used multimeter and tested power going to 1 and 7 fuse. Both good.

Used multimeter to get readings off coil with key on and good.

So I reconnected the rpm relay and went to start car. Started and bogged down like before.... motor quit after brief start.

So I got the brilliant idea that the car was sounding like the fuel mixture was not right. I turned the CO adjustment screw .25 turns clockwise. Went to start and it started....and stayed running!

However it runs like crap now and has an erratic idle/hunting from like 700-900 rpm...like a nervous tick.

So I hooked up my dwell meter and I'm not getting a reading. I've done this before and double checked my connections, and still the dwell needle did not move. All this while the car was on it's erratic idling. After about 10 mins with no reading I shut it off.

So now I know it's not a fuel pump issue, and coil is ok.

I'm thinking its now on to lambda? Frequency valve? O2 sensor?

Any thoughts appreciated. Thanks.

[David T]

Ok, so it turns out I got my fuel pump to run when I jumped the relay using 30, 87. All the fuel pump connections are good.

Used multimeter and tested power going to 1 and 7 fuse. Both good.

Used multimeter to get readings off coil with key on and good.

So I reconnected the rpm relay and went to start car. Started and bogged down like before.... motor quit after brief start.

So I got the brilliant idea that the car was sounding like the fuel mixture was not right. I turned the CO adjustment screw .25 turns clockwise. Went to start and it started....and stayed running!

However it runs like crap now and has an erratic idle/hunting from like 700-900 rpm...like a nervous tick.

So I hooked up my dwell meter and I'm not getting a reading. I've done this before and double checked my connections, and still the dwell needle did not move. All this while the car was on it's erratic idling. After about 10 mins with no reading I shut it off.

So now I know it's not a fuel pump issue, and coil is ok.

I'm thinking its now on to lambda? Frequency valve? O2 sensor?

Any thoughts appreciated. Thanks.

Make sure you are getting power to the Lambda ECU and the frequency valve is buzzing when the motor is running. Once you get the valve to buzz you will have to set the mixture screw back where it was.

[Bitsyncmaster]

A 1/4 turn is a lot. That may drive the FV to the extreme but even so the meter should read. I still suggest you try the bulkhead connector trick (unplug and plug back in).

[Beachdrifter]

A 1/4 turn is a lot. That may drive the FV to the extreme but even so the meter should read. I still suggest you try the bulkhead connector trick (unplug and plug back in).

Thanks for the suggestion, which ones ...to the right of the ignition coil?

Also I took a picture of my RPM relay. I have a green one by KAE , made in Germany. Is this a new type or old original ?

This is what it looked like. It had some brownish crusty stuff underneath which I gently wire brushed.. I'm ordering new one from Hervey tomorrow.2394423945

[Kenny_Z]

I have a green one from Hervey but I don't use it. Whenever it's installed the car runs terribly. I have my original still running the car and the green one as my backup.

[DeLorean03]

Thanks for the suggestion, which ones ...to the right of the ignition coil?



I'm betting the yellow bulkhead connector.

Go to this link, click on the pdf files associated with it. Save it on your computer just to be safe. This kind of info is invaluable - especially if Talk were to ever go down again.

http://dmctalk.org/showthread.php?40-All-Wiring-Schematics&p=7640&viewfull=1#post7640

[Bitsyncmaster]

Thanks for the suggestion, which ones ...to the right of the ignition coil?

Also I took a picture of my RPM relay. I have a green one by KAE , made in Germany. Is this a new type or old original ?

This is what it looked like. It had some brownish crusty stuff underneath which I gently wire brushed.. I'm ordering new one from Hervey tomorrow.2394423945

That light green case, light green connector is the one unit I can not use to update with my circuit board. They used a different footprint layout on the connector.

[Beachdrifter]

Thanks all. So I disconnected all the bulkhead connections and plugged them back in, and same.

Today I'm going to get some readings off the CPR/WUR and frequency valve. I suppose disconnecting these while the car is on to read voltage. This should tell me for sure if RPM relay is doing its job.

Also no dwell reading , so I suspect fuel issue .

This is unbelievable , car ran perfect a few days ago, now it's like the car can barely start and idle without fidling with the co screw .

[Bitsyncmaster]

The RPM relay also needs to power the "main fuel relay" also known as the lambda relay. So it could still be a faulty RPM relay. You can test if that's the problem with a three way jumper on the RPM relay socket.

[Beachdrifter]

The RPM relay also needs to power the "main fuel relay" also known as the lambda relay. So it could still be a faulty RPM relay. You can test if that's the problem with a three way jumper on the RPM relay socket.

Thanks Dave ,that was a great idea. I did just that. I heard the fuel pump buzzing and also could hear the frequency valve clicking. So I imagine the Lambda was getting power.

I went to start the car but it would only crank, not start at all.

So I plugged the Rpm relay again and turn the key to the on position. Normally this causes the fuel pump to buzz momentarily, but after several key turns I didnt hear anything. I tried again after I took the relay in and out of plug a few times. Then I could hear the pump buzz.

I was able to start the car only with the rpm relay plugged in, but the car runs like total crap and when I press gas it will bog down and does not rev up. With my dwell meter hooked up still I did notice the needle move up and be steady at 50% (2x 8 cyl). No attempt to hunt like it normally does during warm up...sounded like a slow almost stalling chug chug chug chug the whole time.

I ordered a few rpm relays from Hervey today and overnighted, as well as a lambda relay. I think it's something with the rpm relay, but car is not starting either even by bypassing it. It feels like the fuel mixture got all messed up somehow.

[Beachdrifter]

Update, I also took the opportunity to take some readings from the CPR/WUR and frequency valve while I had the RPM relay jumped with power.

CPR/WUR -
Voltage = 12 v.
Resistance = 20-21 ohms across contacts on unit.

This tells me the heater element and power going to the WUR is normal, so the unit should be good and should not be a source of my problem.

-----------------

Frequency valve -
Voltage on 1 pin - 12 volts , this must be the main power from lambda relay.

Voltage on 2nd pin - .29 volts , this must be coming from the lambda ecu

I hear the frequency valve clicking, and I assume these readings are nominal so it must be good.

=============

So tomorrow I should be getting my new rpm relays and trying them. The current rpm relay is what seems to be working intermittingly.

I assume my fuel system is working fine, because last time I started the car and it ran like a champ was saturday.

If the new rpm relay does nothing, I will swap out my lambda ecu with a known good spare one I have.

[Beachdrifter]

So today i put a new RPM relay and engine cranks but no start.

I measured the voltage on both sides of coil and Im getting a reading of .69 volts on both sides.

Im thinking I have an ignition problem because that doesn't seem right at all.

Could it be a faulty ignition ECU ?

[hmcelraft]

When the key is in the start position the ignition is charged with a higher voltage to the coil by energizing only half the ballast via a connection to a relay in the engine compartment under the ballast. After the engine starts and the key is released to the run position the ignition is charged through the entire ballast via a wire from the an aux power relay in the fuse compartment. Sounds to me like the engine start circuit works but the run circuit does not. You probably broke the connection somehow to the run side of the ignition ballast or the top half of the ballast isn't functioning for some reason.

The RPM relay signal from the coil could be weak - be sure of you have good connections there from the coil - no broken or loose wires, etc.

Harold McElraft - 3354 et.al.

[Bitsyncmaster]

Your + side of the coil should have 3 to 6 volts if the engine is stopped and the - side is ground (grounded via ECU).

So your ballast resistor open, a wire connection open or your coil is shorted.

[Beachdrifter]

Your + side of the coil should have 3 to 6 volts if the engine is stopped and the - side is ground (grounded via ECU).

So your ballast resistor open, a wire connection open or your coil is shorted.

Thanks guys, Interesting, so I swapped the ignition bypass relay on the bulkhead with the same type relay of the low beam.

I went to crank the car and engine actually started each time, but then immediately dies. I measured the + side of coil with key on this time and got 4.5 v.

Each time I hear the fuel pump buzz when I turn the key too, so it seems the coil is sending enough voltage to rpm relay this time.

So now if I can keep the car running. Ive determined my Cpr and freq valve is good. Car is cold and turning on so cold start valve must be doing its thing too.



Now if I can keep the car running...

[David T]

Thanks guys, Interesting, so I swapped the ignition bypass relay on the bulkhead with the same type relay of the low beam.

I went to crank the car and engine actually started each time, but then immediately dies. I measured the + side of coil with key on this time and got 4.5 v.

Each time I hear the fuel pump buzz when I turn the key too, so it seems the coil is sending enough voltage to rpm relay this time.

So now if I can keep the car running. Ive determined my Cpr and freq valve is good. Car is cold and turning on so cold start valve must be doing its thing too.



Now if I can keep the car running...

Since you are mucking around the ballast resistor you can try this. The metal tabs that the wire connectors attach to are steel and they can rust. Take the wires off one at a time and clean up each connection. It could be you are getting ignition power during cranking (the bypass resistor is supposed to be cutting out 1/2 of the ballast resistor during cranking) but as soon as you release the key from the start position and the starter motor stops, the ballast resistor no longer is bypassing 1/2 of the ballast resistor and you lose ignition power because of a bad connection. Another remote possibility is you moved a connection around on the ballast resistor and now the motor will only run during cranking. Check that each wire is where it is supposed to be. Or maybe 1/2 of the ballast resistor is bad? The 1/2 that is necessary for run.

[Bitsyncmaster]

Your not getting voltage on the white wire to the resistor or the resistor is bad. That is how I test the bypass circuit. I pull the white wire, start the engine and it will die when you release the key.

[Beachdrifter]

So onto the ballast resistor . Is there a specific test on it to tell if it's good or bad? I took it out and have a few pics of the tips. One tip looks burnt in the center but not sure if that's normal.

Thanks.

[hmcelraft]

You can run a hot feed (like a jumper from the positive battery post by the coolant reservoir) to the coil wire feed from the ballast resistor and the engine should run all the time if there is an issue with ballast or the run feed to the ballast. While the key is in the run position you should measure the voltage of the run feed to the ballast. It should be battery voltage.

Harold

[hmcelraft]

If you run the engine in "ballast jumper" mode for too long it may damage the coil and distributor cap. I would keep it to 5 or 10 minutes at a time - tops.

Harold

[Beachdrifter]

Your not getting voltage on the white wire to the resistor or the resistor is bad. That is how I test the bypass circuit. I pull the white wire, start the engine and it will die when you release the key.

Thanks Dave and Harold. I measured the voltage to the resistor with key on , at the top right ballast prong and measured about batt voltage. The prong just below it was about half... probably the resistor doing its job?

Of course the left prong was negligible since its only on during cranking...which works because car does initially start.

I will try doing the jump test tomorrow to see if it will start and stay on.

Thanks.

[Bitsyncmaster]

Thanks Dave and Harold. I measured the voltage to the resistor with key on , at the top right ballast prong and measured about batt voltage. The prong just below it was about half... probably the resistor doing its job?

Of course the left prong was negligible since its only on during cranking...which works because car does initially start.

I will try doing the jump test tomorrow to see if it will start and stay on.

Thanks.

Something is wrong. Yes the left side only gets power during cranking but it still will show voltage since it should be an open circuit on the wire but the resistor connects it to the right side. But about half voltage on the right side is correct.

You should have read about 3/4 of battery voltage on the left side. Maybe your meter probe did not make connection.

[Beachdrifter]

Something is wrong. Yes the left side only gets power during cranking but it still will show voltage since it should be an open circuit on the wire but the resistor connects it to the right side. But about half voltage on the right side is correct.

You should have read about 3/4 of battery voltage on the left side. Maybe your meter probe did not make connection.

Thanks Dave, yes you are correct I do get some voltage on the left side as well with key on, sorry.

So today I will try to jump the coil to see if it stays on. Curently the car starts everytime but will not stay on and dies after 1-2 second. I also have a new coil (but tried on my old coil too and same).

And at this point I'm seriously thinking I have an Ignition ECU malfunction. Looking for one to swap out with.

[Bitsyncmaster]

Thanks Dave, yes you are correct I do get some voltage on the left side as well with key on, sorry.

So today I will try to jump the coil to see if it stays on.

And at this point I'm seriously thinking I have an Ignition ECU malfunction. Looking for one to swap out with.

If your engine starts, I don't think your Ignition ECU would be bad. Now you may have an intermittent problem. So even though you read correct voltage on the resistors now, sometimes those readings may not be correct.

I had an intermittent when I first bough my car. That problem was the connector on the distributor pickup wire. It was the worst corrosion problem I've ever seen. I removed that connector and spliced the wires.

[rdarlington]

Probably not related, but my car was doing something similar a while back. The electrical connection on the this thing was causing me grief:

http://2.bp.blogspot.com/-ZGi3uhzgoNI/UItcUXIEwYI/AAAAAAAABTs/uPR1Q7Rk-Q0/s1600/IMG_3910.JPG

When connected, no problems. When disconnected the car would start up and then immediately stall. It would not run at all. The electrical spade connectors were pushed up inside the rubber boot and making intermittent contact. I've since slid them out and gave em a little squeeze to tighten em up. This connector is easy to knock loose if you're back there pulling at other things.

-Bob

[Beachdrifter]

Probably not related, but my car was doing something similar a while back. The electrical connection on the this thing was causing me grief:

http://2.bp.blogspot.com/-ZGi3uhzgoNI/UItcUXIEwYI/AAAAAAAABTs/uPR1Q7Rk-Q0/s1600/IMG_3910.JPG

When connected, no problems. When disconnected the car would start up and then immediately stall. It would not run at all. The electrical spade connectors were pushed up inside the rubber boot and making intermittent contact. I've since slid them out and gave em a little squeeze to tighten em up. This connector is easy to knock loose if you're back there pulling at other things.

-Bob

Thanks for mentioning it. What actually goes connected on those two little prongs? They look like electrical connections. I checked my car and I don't have anything connected to them.


My ignition ecu swap did nothing to change my situation and seems nothing is working.

I'm at a dead end, and worn out for now. If anyone else has experience the start and die issue, I'm willing to try anything.

[rdarlington]

Thanks for mentioning it. What actually goes connected on those two little prongs? They look like electrical connections. I checked my car and I don't have anything connected to them.


My ignition ecu swap did nothing to change my situation and seems nothing is working.

I'm at a dead end, and worn out for now. If anyone else has experience the start and die issue, I'm willing to try anything.

There is a rubber connector with 2 pins that mate that somehow connect back to the idle speed switch. I'm not clear on the operation though. My best guess is that this thing shuts off the vacuum advance line to the distributor when the car is idling.

The connector line goes back to a "Y" which is also connected to the white connector on the rear firewall. See pics. Also, keep in mind that I have my rubber boot slid back so I know for sure I've got a good connection. Normally there would not be wires coming out of this boot.

Connection to solenoid:
24025


And this is the connector that if you follow down will go to a Y in the cable, and if you keep going it will end up at the above connector:
24026

[Beachdrifter]

Hi all. so here is the latest.

When i disconnect the idle speed regulator the car starts and stays idle at around 600 rpm. If i try to give it gas it dies again.

When I reconnect the idle speed regulator it will start but will not idle.

i also noticed the tube from the underside of the idle speed regulator going to the fuel distributor end is very loose, to where i can move it side to side with my hand. Any idea where this tube is connected to?

Thanks.