My Delorean is cursed!

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After a complete overhaul of my D's fuel system it's been working fine for the past 6 months but three days ago suddenly for no reason she became hard to start. It didn't seem to matter whether she was hot or cold it would take me holding the starter down for a prolonged period to get her to fire. If the battery started to get weak, I would have to pull the air cleaner and shoot some starter fluid into the intake to have her fire up. When I finally had time to diagnose the problem it suddenly disappeared! Now I can't make her not start up on the first crank. Has anyone also experienced similar problems before? It's like my car is cursed or something, I really can't trust it to take longer trips because of problems like this, it's my daily driver but only for local destinations due to these types of problems.

[Bitsyncmaster]

Since it started with starting fluid, you must have an intermittent with the fuel system. But if it's only happening during starting (runs fine once started) that make it harder to trouble shoot.

Maybe an electrical problem with the fuel pump. RPM relay, bad connection, bad inertia switch.

You can test the voltage at the fuel pump to find bad connections. Voltage should be about 1 volt below battery voltage.

You can carry a jumper to bypass the RPM relay once the problem occurs.

[hmcelraft]

You may have gotten a bad load of fuel!

[David T]

You may have gotten a bad load of fuel!

First thing I would check is that the frequency valve is buzzing. Next would be the cold start valve is squirting when cranking cold.

[Henrik]

Looking thru my files I found this really good troubleshooting procedure; not sure where it came from but it might Warren Wallingford @ DMCH.35018

[Jason]

My car used to behave kind of like that when I first bought it. Sometimes for no apparent reason it would refuse to start, but a shot of starter into the air intake would get it going.

The problem turned out to be bad ground cables. There was enough voltage drop under load that the starter would be just barely turning the engine fast enough to start. It took a long time to figure out because I had spark, had fuel, and hadn't been around other DeLoreans enough to notice a difference in cracking speed.

Running a nice thick wire from the negative terminal of the battery to the engine (and later removing the "hack" wire and replacing all the main ground cables) fixed the starting problems.

[[email protected]]

Thanks for all the input guys, seems my weekends are going to be busy once again. Also the PDF on electrical troubleshooting is great, we need more articles like that.

[David T]

Thanks for all the input guys, seems my weekends are going to be busy once again. Also the PDF on electrical troubleshooting is great, we need more articles like that.

Aren't you going to tell us what you found or are you going to keep us all in suspense?

[mluder]

You can test the voltage at the fuel pump to find bad connections. Voltage should be about 1 volt below battery voltage.



So... This is interesting. A friend and I were trying to diagnose a misfire/fluctuating RPM in my car and we read a lower voltage (<12 V) at the fuel pump and thought it might be indicative of a voltage drop which could result in poor fuel pump performance. So it's typical for voltage here to be less? Is there a resistor somewhere that reduces voltage intentionally?

Cheers
Steve

[Bitsyncmaster]

So... This is interesting. A friend and I were trying to diagnose a misfire/fluctuating RPM in my car and we read a lower voltage (<12 V) at the fuel pump and thought it might be indicative of a voltage drop which could result in poor fuel pump performance. So it's typical for voltage here to be less? Is there a resistor somewhere that reduces voltage intentionally?

Cheers
Steve

That 1 volt drop is due to all the wire in the harness. If you have more drop than that, you get one long test lead for your multimeter, use that long lead on the battery + terminal and start tracing the voltage drops. You would start at the RPM relay then move to the fuel pump. Then use that long test lead on the battery ground terminal and see how much drop you get on the ground side of the fuel pump. There are connectors that can introduce drops if the pins are not clean and tight.