Fuel Pressure Build Up

[Ricker]

Is it possible to jumper the relay so that the fuel pump runs whenever the key is turned on but the engine is not running? Will this burn up something? I'm tired of hitting the switch over and over again to run the pump 20 - 30 times to pressurize the fuel system after the car sits for 2 weeks. I have replaced the fuel pump, check valve, accumulator, and O-rings in the pressure regulator. Not sure if there is anything else to try. I can't find the minute pressure leaks. Once the pressure is built up, the car starts fine hot or cold.

[Bitsyncmaster]

Is it possible to jumper the relay so that the fuel pump runs whenever the key is turned on but the engine is not running? Will this burn up something? I'm tired of hitting the switch over and over again to run the pump 20 - 30 times to pressurize the fuel system after the car sits for 2 weeks. I have replaced the fuel pump, check valve, accumulator, and O-rings in the pressure regulator. Not sure if there is anything else to try. I can't find the minute pressure leaks. Once the pressure is built up, the car starts fine hot or cold.

You could jumper the RPM relay socket but it would put a heavy load on the key on circuit and prevent the safety measures of the RPM relay. It only takes about 2 seconds of the pump running before the PPR regulator starts to feed return fuel. So any further priming would do nothing.

[Helirich]

I?ve been driving mine less recently. Like once a month. I don?t have to switch it multiple times. Something wrong there.

[Ricker]

You could jumper the RPM relay socket but it would put a heavy load on the key on circuit and prevent the safety measures of the RPM relay. It only takes about 2 seconds of the pump running before the PPR regulator starts to feed return fuel. So any further priming would do nothing.

But I don't understand why, after the car sits for a week or so and only on long idle times, does it take 20 - 30 primes of the fuel pump to get gas to the engine fuel injection system? A day or two there is no issues, it holds pressure and fuel. It is like the fuel in the line from the front fuel pump to the engine goes empty.

[Bitsyncmaster]

But I don't understand why, after the car sits for a week or so and only on long idle times, does it take 20 - 30 primes of the fuel pump to get gas to the engine fuel injection system? A day or two there is no issues, it holds pressure and fuel. It is like the fuel in the line from the front fuel pump to the engine goes empty.

Do the cold start valve test. Put the CSV into a jar and pull the white/yellow wire off the resistor block so it won't start. Crank the engine and see if you get any fuel in the jar.

My car does need the CSV working after it sits for a week or more. Otherwise it starts right up without needing it.

[Ricker]

Do the cold start valve test. Put the CSV into a jar and pull the white/yellow wire off the resistor block so it won't start. Crank the engine and see if you get any fuel in the jar.

My car does need the CSV working after it sits for a week or more. Otherwise it starts right up without needing it.

I let the car sit for a week or so to make sure it would not start right off that way I could do the checks. Wouldn't you know it, it started right up. Try again next week.

[Ricker]

I let the car sit for a week or so to make sure it would not start right off that way I could do the checks. Wouldn't you know it, it started right up. Try again next week.

So, I tried to start the car again today as it has set for a few days. It did not start so I then took the grey plug from the warm-up regulator and put it at the blue plug on the cold start valve. It started right up. Not sure what that means? Could it be the termo time switch or could it be the engine temperature senor? How would you check both? Thanks!

[Ron]

So, I tried to start the car again today as it has set for a few days. It did not start so I then took the grey plug from the warm-up regulator and put it at the blue plug on the cold start valve. It started right up. Not sure what that means? Could it be the termo time switch or could it be the engine temperature senor? How would you check both? Thanks!Swapping the two plugs is one of the tests to check the TTS. (It sends power to the cold start valve.) The engine temperature sensor has nothing to do with the cold start valve (its for the gauge only).
Sounds like the termo time switch (TTS) might be bad. Do a search to find other tests you can perform before purcha$ing one...

[AugustneverEnds]

If you do need a thermotime switch they are not too pricy (https://store.delorean.com/102125-thermotime-switch.html) $56.12 plus $8.99 for the adapter to make it fit (https://store.delorean.com/102122-screwed-adapter.html). If you have to have an OEM one then that's a more difficult and expensive matter.

[Ricker]

Well, I got out today and tested the Thermo Time Switch. With the engine as ground, the one pin read 0 ohms, the other 30 ohms. It doesn't look like that is the problem. And since the car has only sat for a day, it started right up. I'll wait a week and try something else. Any ideas? It still seems like the fuel in the line from the fuel pump to the engine goes away. Where, I don't know. No marks on the garage floor or gas smells.

[Bitsyncmaster]

There is a lot of wiring that can make the CSV not fire. My car had 50 ohms in a bulkhead connector going to the CSV circuit. It never fired until I fixed that.

Your best bet is to pull the CSV, put it in a jar and test that it releases a little fuel on cranking a cold engine. If it does you may not have a CSV problem or you have an intermittent problem with it.

[82DMC12]

Do what Dave McKeen says first - pull the CSV out , put in a jar, and turn the key. I would remove the coil wire from the ignition coil first so the car doesn't start trying to run. You just want to see if the CSV is spraying into the jar. If it does, try pinching the female pins in the blue plug closed a bit so they make a better connection. Might just be the plug.

If that still doesn't work and it takes a lot of effort to start after a few days, you might have injectors leaking down at rest. You'll have to pull all the injectors out and try this:

1) Get a medium sized mason jar for each injector. Drill a hole in the lid so the injector fits in just right.
2) Jump the RPM relay and check for injectors dripping into the mason jars. If they are, the CO screw could be too rich. If not, press down on the air flap about 1/3 of the travel and make sure all the injectors start and stop simultaneously. Make sure the spray pattern is a fine mist, atomized fuel, and shaped like an umbrella. When the plate isn't pressed the down, the injectors should not drip. When you are satisfied, while the fuel pump is still running, wipe off the tip of each injector with a non-linting rag so the tip is dry.
3) Dump out the jars and wipe them clean, placing the injectors back into the jars one at a time.
4) remove the pump jumper wire and let the injectors sit in the jars. Check the injectors after 30 minutes and see if any of them are damp. Maybe they even dripped a bit of fuel into the jar. They should be bone-dry if they don't leak down.

If any of the injectors are dripping, I would just replace all of the injectors with a new set of 022 Bosch injectors.

Following this procedure fixed my similar issue (replaced all the injectors after confirming one or two were leaking down over a long period of time).

[Ricker]

Do what Dave McKeen says first - pull the CSV out , put in a jar, and turn the key. I would remove the coil wire from the ignition coil first so the car doesn't start trying to run. You just want to see if the CSV is spraying into the jar. If it does, try pinching the female pins in the blue plug closed a bit so they make a better connection. Might just be the plug.

If that still doesn't work and it takes a lot of effort to start after a few days, you might have injectors leaking down at rest. You'll have to pull all the injectors out and try this:

1) Get a medium sized mason jar for each injector. Drill a hole in the lid so the injector fits in just right.
2) Jump the RPM relay and check for injectors dripping into the mason jars. If they are, the CO screw could be too rich. If not, press down on the air flap about 1/3 of the travel and make sure all the injectors start and stop simultaneously. Make sure the spray pattern is a fine mist, atomized fuel, and shaped like an umbrella. When the plate isn't pressed the down, the injectors should not drip. When you are satisfied, while the fuel pump is still running, wipe off the tip of each injector with a non-linting rag so the tip is dry.
3) Dump out the jars and wipe them clean, placing the injectors back into the jars one at a time.
4) remove the pump jumper wire and let the injectors sit in the jars. Check the injectors after 30 minutes and see if any of them are damp. Maybe they even dripped a bit of fuel into the jar. They should be bone-dry if they don't leak down.

If any of the injectors are dripping, I would just replace all of the injectors with a new set of 022 Bosch injectors.

Following this procedure fixed my similar issue (replaced all the injectors after confirming one or two were leaking down over a long period of time).


Ok. I,let the car sit for a few days. Pulled the CSV and placed it into a jar. Had my wife turn the key and it sprayed immediately in a nice fine mist, umbrella shape. So I don't think it is that or the TTS as it ohmed out Ok. I will try the injectors next as you suggested. Is it possible then, if the injectors can leak, can the CSV leak and do the same thing or just the injectors? Do you replace all injectors or just the one(s) that are bad? I did have them sent out years ago (about 5,000 miles ago) and tested. Said they were all good. Nevertheless, I'll do the testing.

Note: I had the fuel/air ratio adjust a few years ago with a 4 as analyzer and a past '80s dealership DeLorean mechanic.

[82DMC12]

Ok. I,let the car sit for a few days. Pulled the CSV and placed it into a jar. Had my wife turn the key and it sprayed immediately in a nice fine mist, umbrella shape. So I don't think it is that or the TTS as it ohmed out Ok. I will try the injectors next as you suggested. Is it possible then, if the injectors can leak, can the CSV leak and do the same thing or just the injectors? Do you replace all injectors or just the one(s) that are bad? I did have them sent out years ago (about 5,000 miles ago) and tested. Said they were all good. Nevertheless, I'll do the testing.

Note: I had the fuel/air ratio adjust a few years ago with a 4 as analyzer and a past '80s dealership DeLorean mechanic.Yes the cold start valve could possibly leak down as well but it's uncommon. It's not subject to the same abuse the other injectors are, plus it is solenoid controlled instead of pressure controlled.

Personally, I replaced all six injectors because I had a full unused set handy.

Sent from my Pixel 6a using Tapatalk

[Ricker]

Do what Dave McKeen says first - pull the CSV out , put in a jar, and turn the key. I would remove the coil wire from the ignition coil first so the car doesn't start trying to run. You just want to see if the CSV is spraying into the jar. If it does, try pinching the female pins in the blue plug closed a bit so they make a better connection. Might just be the plug.

If that still doesn't work and it takes a lot of effort to start after a few days, you might have injectors leaking down at rest. You'll have to pull all the injectors out and try this:

1) Get a medium sized mason jar for each injector. Drill a hole in the lid so the injector fits in just right.
2) Jump the RPM relay and check for injectors dripping into the mason jars. If they are, the CO screw could be too rich. If not, press down on the air flap about 1/3 of the travel and make sure all the injectors start and stop simultaneously. Make sure the spray pattern is a fine mist, atomized fuel, and shaped like an umbrella. When the plate isn't pressed the down, the injectors should not drip. When you are satisfied, while the fuel pump is still running, wipe off the tip of each injector with a non-linting rag so the tip is dry.
3) Dump out the jars and wipe them clean, placing the injectors back into the jars one at a time.
4) remove the pump jumper wire and let the injectors sit in the jars. Check the injectors after 30 minutes and see if any of them are damp. Maybe they even dripped a bit of fuel into the jar. They should be bone-dry if they don't leak down.

If any of the injectors are dripping, I would just replace all of the injectors with a new set of 022 Bosch injectors.

Following this procedure fixed my similar issue (replaced all the injectors after confirming one or two were leaking down over a long period of time).

It has taken me some time to do the injector test. What a discovery. One injector had a bad looking spray. Not all did the same amount. Once I cleaned/dried the injector tips and waited about 15 minutes one sprayed, 3 others were wet and one dripped. So, it looks like some new injectors are in my immediate future (along with the clips and rubber seals). Thanks for the direction!

[Timeless]

So, it looks like some new injectors are in my immediate future (along with the clips and rubber seals). Thanks for the direction!
I may have a set for sale. They are new and purchased in 2023 but only used ~30 miles before I decided to go EFI. If you're interested I'll let DPI know to keep them (if they still have them) and when my car returns from DPI I'll gladly send them to you.

[Ricker]

I may have a set for sale. They are new and purchased in 2023 but only used ~30 miles before I decided to go EFI. If you're interested I'll let DPI know to keep them (if they still have them) and when my car returns from DPI I'll gladly send them to you.
Sorry, I already ordered them from Deloreango.com yesterday and they have already shipped (got the notice this morning).

[Timeless]

Sorry, I already ordered them from Deloreango.com yesterday and they have already shipped (got the notice this morning).
All good! :thumbup2:

[Ricker]

Well I got the new fuel injectors from Deloreango and installed them this morning. Car started up right away and ran very nice and smooth. Let it run for a while at idle but it the idle did increase (which has been typical went in park). Turned it off. Went out 20 minutes later and nothing. Won't start or even fire. I touched nothing else. It ran, I turned it off, and now nothing. I let it sit for a while to cool off and still nothing. Any ideas? What could I have done. The fuel pump is running.

[Bitsyncmaster]

Any change to components in the fuel system would require the need to check mixture via dwell.

[Rich]

Do you mean the engine DID crank over strongly, as usual, but didn't start? And it didn't sound like it was almost starting while you cranked it ("won't even fire")?

Did you try it again later when the engine was fully cold?

[Ricker]

Do you mean the engine DID crank over strongly, as usual, but didn't start? And it didn't sound like it was almost starting while you cranked it ("won't even fire")?

Did you try it again later when the engine was fully cold?

After the new injectors the car ran fine. Drove it out of the garage and parked it on the road. Turned it off. Came back 20 minutes later and it will turn over but will not fire at all. Tried turning the key numerious times to build up fuel pressure - still nothing. I did nothing from when it was running to when it won't except to turn the key. Grrrrr.

[Ron]

I agree that you should always check the dwell after changing injectors. To get it running so you can, try a shot of starting fluid under the air plate. If no luck, put an spare plug wire in the coil and see if it sparks to ground.

[Ricker]

So, I went out and tried it again. Started right up after me doing nothing. Let it set for 20 minutes, started right up again. I'll let it set a day or so and see what happens. Hoping it starts AND solved the initial problem of fuel pressure loss.

[82DMC12]

You still may need to adjust the mixture screw though. I just replaced my injectors with exactly the same model injectors as I previously had and ended up having to turn my mixture screw about a quarter turn to get the dwell meter reading perfect again.

As for the car not starting when hot, you can have a hot start problem that is undiagnosed.

Sent from my Pixel 6a using Tapatalk

[Ricker]

I replaced all the injectors after it appeared some were bad. I let the car sit for a few days to see if that helped. It did. Engine fired up right off. It looks like the original leaky injectors were the problem all along. Thanks for all the info and ideas. I feel good after checking all the other items.