Weird cold and hot start issues

[Bitsyncmaster]

That's normal -- The injectors open at 50-60 PSI.

I thought they opened at 40 PSI but that may be counting the engine vacuum.

[Jonathan]

It seems like my thermo time switch is damaged.

Did you ever fix or replace the thermo time switch?

http://support.delorean.com/kb/a60/c...rt-issues.aspx

[82DMC12]

Vacuum leaks can be hard to find, especially minor leaks. I suggest borrowing or buying a smoke machine. Seal the air meter flap with a latex balloon and large zip tie. Then plug the smoke machine into the PCV / metal mesh cap. Let 'er rip and you'll very quickly find any vacuum leaks. Eventually the smoke has to go somewhere if you keep pumping it in and it will start to exit the oil dipstick tube, but that's OK.

Fix all the leaks, but also check for proper vacuum routing AND make sure the vacuum solenoid is working (no vacuum to the distributor when the car is at idle). The vacuum system, and how it changes depending on idle on/ idle off and engine hot / cold is all explained in the shop manual in the Fuel & Emissions section.

[Ron]

I thought they opened at 40 PSI but that may be counting the engine vacuum.

FWIW- I remember it by 55 +/- 5 PSI Manual says 3.5 to 4.1 Bar.

[Magnus86]

Vacuum leaks can be hard to find, especially minor leaks. I suggest borrowing or buying a smoke machine. Seal the air meter flap with a latex balloon and large zip tie. Then plug the smoke machine into the PCV / metal mesh cap. Let 'er rip and you'll very quickly find any vacuum leaks. Eventually the smoke has to go somewhere if you keep pumping it in and it will start to exit the oil dipstick tube, but that's OK.

Fix all the leaks, but also check for proper vacuum routing AND make sure the vacuum solenoid is working (no vacuum to the distributor when the car is at idle). The vacuum system, and how it changes depending on idle on/ idle off and engine hot / cold is all explained in the shop manual in the Fuel & Emissions section.

Where do i find the PCV metal mesh cap? Sorry if i ask, but i cant translate pcv into german and i'm not sure what to look for. Furthermore: Could a vacuum leak really causea no starting engine? I would suggest this must be a pretty big vacuum leak then?!

[82DMC12]

Sorry, we call it PCV (positive crankcase ventilation) but I don't think it's actually referred to that in the manual.

It's the black cap you have to remove to add oil to the engine.

A major vacuum leak could cause the engine to fail to start under all conditions, but probably not intermittently like you have. Still, all vacuum leaks should be corrected because any vacuum leak will interfere with the fueling system. There are so many things that work together and have to be working properly in order for good reliable starting and running. Ignition, fuel, vacuum lines, a few electrical switches, and mechanical adjustments like the throttle.



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[Magnus86]

Ah thank you.
Well i did notice that the oil cap itself isn?t sealed very well as the O-Ring seems to be worn. When the cap is fully closed i can jiggle it around a bit. Is a vacuum leak there also a problem?

Regarding the Vacuum i did a first check:
There is this one ?closing valve? (don?t know the english word) that goes inside the WUR. I removed this one (rubber hoses pretty stiff) and sucked on the vacuum side of the hose, the black side of the valve. I noticed that it didn?t really holds the vacuum. There is some Vacuum but it slowly gets loose. When i close the other side of the hose (white part of the valve) with my finger and i suck on the black?s side hose i could feel that i got some vacuum on my finger building up. I don?t know if this piece needs to be completely tight? I also tried it the other way: Put the black side of the hose inside a jar of water and blew inside the hose on the white side. I could easily see bubbles coming out of the hose on the black side. I?m not sure if this thing needs to be a 100% tight:

4615840B-A5C7-4FDA-A6DA-15C8353DE2C1.jpg



Another test i did today:
I checked the control pressure, so i opened the valve to the WUR and let the fuel pump prime. With the fuel pump priming i got about 13PSI:

2C9EABC6-920A-4E8E-A77A-320736C5D2D8.jpg

Right after i turn of the fuel pump the pressure goes up to roughly 23PSI:

9C1F03F6-0B9C-4047-AF42-5541656F2998.jpg

Aaand after about an hour i got 20PSI:

3070D1DA-B46D-4628-B61B-35D6AAAED71D.jpg

This is how my fuel gauge is hooked up for the control pressure test:

951DFDB4-7010-4CA2-9BED-96DE4F71C92F.jpg

All those tests are with a cold and not running engine as i still wait for my new fuel lines.
Are those values i got for rest pressure good?

Oh and i tried again pushing the air plate down while having a good rest pressure. The pressure didn?t change in any way after i pushed the plate down.

[Magnus86]

Hey guys,

as i'm still waiting i did another test today with the rest pressure.
Strangely, today my primary pressure wasn't at 70 PSI but more around 60-65PSI. I couldn't find any leaks in my pressure-gauge hoses. What could be the problem when on some day the primary pressure is at 70 PSI and on another day it's just 60PSI?

As i said i replaced the O-Rings of the pressure valve inside the fuel distributor..is there something i can mess up here?
Furthermore the pressure dropped way faster than a few days ago. Starting at 60PSI the pressure dropped down to 15PSI in just 1 hour and 30 minutes.

A few things i noticed:
My fuel pump was a bit wet on top of it's head, since the car hasn't been driven for quite some days it seems like it's slightly leaking. I let the fuel pump prime but didn't see anything. I think one of the new copper washers isn't tightened enough. Can someone tell me whats the correct torque for the fuel pump banjo bolt?

But as far as i understand, the (sometimes) slightly leaking fuel pump would not be a problem for the rest pressure as the fuel accumulator and the pressure valve in the distributor should stop the fuel from returning to the fuel pump right?

Another question:
As mentioned earlier it seems like one of my fuel lines is leaking. Strangely this doesn't happen all the time and sometimes the line is completely "dry". Of course i'll replace the fuel lines anyways. I heard that a leaking fuel line to the injectors could cause a pressure loss. But how is that possible? As far as i understood, when the fuel pump is off with rest pressure and the plunger is in it's resting position, it closes all the fuel injector lines and thus, a leaking injector or fuel line wouldn't cause a drop in rest pressure. Or am i getting something wrong here?

I thought about this because i had one injector removed to get it cleaned or replaced (bad spray pattern) and even though the fuel line with the missing injector was completely "open", there was no drop in fuel pressure and no fuel coming out of the fuel line (of course as long as i didn't push the air flap), even with 40 PSI rest pressure.


Another thought i had:
Could a clogged fuel filter (the one next to the fuel accumulator) cause my cold/hot start problems?
But with a clogged fuel lifter there should be a problem with the running engine or driving around as well?
That's not the case, as soon as the engine runs everything is fine.

Thanks a lot

[Bitsyncmaster]

Your original type fuel pump the banjo fitting is after the check valve. So yes a leak at the banjo would reduce rest pressure time but not affect primary pressure tests.

[Magnus86]

Hello there,

so i finally got my new fuel lines mounted and replaced one injector that had a pretty bad spray pattern. Before i mounted the injectors back into the intake i put them into the jars with the new fuel lines to verify that they are all spraying (jumpered rpm relay and push down the air plate). Everything works fine there.

But i still get the problem with starting issues and slowly i'm running out of ideas.

One thing i noticed with my hot start issue..maybe some of you have an idea what could be the problem here:
When i crank the hot engine after a few minutes of sitting most of the time it won't start. I noticed that i have pretty good pressure on the air plate and my gauge is reading 40-45psi rest pressure (valve to the WUR opened for the gauge). So what i did was i unplugged one of the injectors, put it inside a jar and let the engine crank. There was no fuel in the jar after cranking, so the injector wasn't spraying even though my gauge showed good rest pressure. I then jumpered the rpm relay to have the fuel pump running all the time and i cranked the engine again. And still..no fuel coming out of the injector.
After that i slightly pushed on the air metering plate while the pump was still running and the injector was spraying. So as a next step i cranked the engine (RPM Relay in place again) and let a friend of mine slightly push down the air metering plate and the engine fired up. It seems like cranking the hot engine doesn't pull down the air metering plate enough to get the injectors to open?
What does the air metering plate should look like when cranking on a hot engine?
Could this be caused by a vacuum leak or maybe the starter is not turning the engine fast enough for enough air to be sucked in?

I removed the fuel distributor to sort out a stuck plunger. I cleaned it with some acetone and put it back in. To me it looks okay (see video below)?



The other thing is that sometimes i completely loose Pressure on the air plate while my gauge still shows some good pressure.
What could be the problem here? Will check the accumulator in the next days and see if there's any fuel coming out of the rear end of the accumulator.

Thanks a lot in advance