5878 not starting

[piprulz]

5878 isn’t starting anymore. It started earlier today with a little white smoke coming out. I tried to start it again later in the day and it cranks but it never turns over. Any ideas? I tried swapping the blue and gray plugs for the cold start fix but that didn’t help.


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[Ron]

If it turns over at a normal speed, you should first see if it is ignition (spark) or fuel keeping it from starting/cranking up.
Pull the main coil wire off of the coil. Connect a spare/used wire to the coil and see if it will jump a spark to the block (any good ground). If it does' try a good shot of starting fluid in the breather box (or under the metering plate inside).

[David T]

Some other quick and simple tests;
Can you hear the fuel pump run?
Is there gas in the tank?
Check the connections on the white ballast resistor on the firewall, they get rusty and then no spark
Do you feel any resistance when you push on the air sensor plate?

[piprulz]

It’s starting intermittently. How do I check if the fuel pump is working? Does it start when you turn the key or when it starts to crank?


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[Bitsyncmaster]

It’s starting intermittently. How do I check if the fuel pump is working? Does it start when you turn the key or when it starts to crank?


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The stock RPM relay will sometimes prime (run the pump for a second when the key goes to on) but otherwise once the engine is cranking the fuel pump starts.

You can test if it always starts by using the jumper in place of the the RPM relay.

[piprulz]

We jumpered out the rpm relay and the pump worked. We put the rpm relay back and the car started. Does that mean the Rpm relay is bad or the fuel pump?


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[DMC-81]

I'd replace the RPM relay first. It's a good time to upgrade to Dave McKeen's solid state units. One of the great features is that it primes the fuel pump every time before you start the car. I highly recommend it.

[David T]

The RPM relay (the OEM one) gets melted solder joints and can become failed or intermittent. A quick fix is to take it apart and resolder the joints. Temporary fix. Replace the RPM relay. You should check the draw on the fuel pump and all of the wiring connections. When the pump starts going bad it overheats circuit #7 damaging the wiring, connectors, and fuseholder and RPM relay.

[Bitsyncmaster]

The RPM relay (the OEM one) gets melted solder joints and can become failed or intermittent.

The problem with the OEM RPM relay is it's made with single sided Printed Circuit Board and the metal relay is soldered to that PCB to make a connection. Heating and cooling breaks those solder joints of the metal frame of the relay to PCB. Not only does that connection go intermittent but it moves the location of one set of points of the relay. The other set of points are also soldered on the PCB but those solder joints don't usually break.

Using a double sided PCB would have probably cured the problem since the holes get plated through the board and provide much more mechanical stress relief. Also designing it to run cool also would help but I've seen other cars that used single sided PCB on switches that also fail at the solder joints. So it is also subject to vibration or movement that breaks the joints, not just heating and cooling.

[David T]

Like much of the electrical system in the Delorean (and most older British cars) the electrical system is not designed with much excess capacity. Between that and connections getting bad as everything gets older it should not be a surprise that you get failures. When things start to draw just a little bit more current than when new, the electrical system gets overloaded. The whole car also was not designed to last 30 years so seeing parts fail is to be expected. The good news is replacement parts are available and in many cases they are better than the original parts.

[Michael]

Like much of the electrical system in the Delorean (and most older British cars) the electrical system is not designed with much excess capacity. Between that and connections getting bad as everything gets older it should not be a surprise that you get failures. When things start to draw just a little bit more current than when new, the electrical system gets overloaded. The whole car also was not designed to last 30 years so seeing parts fail is to be expected. The good news is replacement parts are available and in many cases they are better than the original parts.
None of that is in the tech manual....therefore all lies!

[piprulz]

I have the new RPM relay from David Mckeen and once every 10 starts or so the fuel pump won’t start. It has 12 volts at the connector but the pump won’t start. We checked the relays and the connections and they seem fine. Can the fuel pump not start sometimes? Can it be something else? I don’t want to spend $400 on a new pump and it doesn’t fix it


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[David T]

Get a voltmeter and see if you have voltage at the pump when the pump doesn't run. A bad connection can cause that to happen. It is also possible the pump is bad.

[piprulz]

Get a voltmeter and see if you have voltage at the pump when the pump doesn't run. A bad connection can cause that to happen. It is also possible the pump is bad.

We have 12 volts at the pump when the pump doesn’t run. Can the pump run sometimes and sometimes not? I thought it either works all the time or it doesn’t


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[AugustneverEnds]

We have 12 volts at the pump when the pump doesn’t run. Can the pump run sometimes and sometimes not? I thought it either works all the time or it doesn’t


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How do the wires at the pump look? Water can gather there and corrode the terminals out. Any clue how old your pump is? If you do need a replacement there are options for far less than $400

[piprulz]

How do the wires at the pump look? Water can gather there and corrode the terminals out. Any clue how old your pump is? If you do need a replacement there are options for far less than $400

I’m not sure if it’s original or not. Which option is the best? Is the $90 one good?


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[Ron]

We have 12 volts at the pump when the pump doesn’t run. Can the pump run sometimes and sometimes not? I thought it either works all the time or it doesn’t


Sent from my iPhone using TapatalkA voltmeter will not tell you if there is enough power getting to the pump...a poor connection in the circuit etc may not supply the amperage needed. A better test is to use a test light (provides a load to draw more amperage). The best is to jumper it straight off of the battery. If it does not run continuously, it is bad.

[AugustneverEnds]

I’m not sure if it’s original or not. Which option is the best? Is the $90 one good?


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https://www.deloreango.com/us/fuel-pump.html

This one has been working fine for me for years now (and I drive quite a bit).

[David T]

If you can measure 12 volts on the pump terminals and it isn't running, it is bad and has to be replaced. Usually they get really noisy before they die but not always. if all of your parts are in good condition the cheapest and fastest repair is to stay with the OEM set-up and just replace the pump.

[piprulz]

If I turn the key once and then twice and then wait until I hear the pump turn on the car starts every time. If I turn the key fast and don’t wait the pump doesn’t start sometimes. Is that an ignition issue?


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[Ron]

If I turn the key once and then twice and then wait until I hear the pump turn on the car starts every time. If I turn the key fast and don’t wait the pump doesn’t start sometimes. Is that an ignition issue?
That sounds like normal operation for most OEM RPM Relays. Basically, Dave's relay keeps it primed. Both turn on the pump when they see an ignition signal. So, pull the coil wire and see if it sparks to ground (it should) when you turn it fast to see if it is an ignition issue...
(Easy way- Use a spare plug wire and connect it to the coil to jump to the block with.)