Hot Start Problem

[Nick H]

Hi All,
        In need of a bit of help please. 
I have been working on the stuttering under load problem on my car.
Good news is that I have completely fixed that problem. Turned out to be injectors and CPR. 
New injectors and CPR sorted it. I also replaced the metering head while I was at it as it had been replaced in the States with a B28F Volvo unit by PO.

I got the CO set at 1.5%. Lambda disconnected.

Car starts perfect from cold. 
Car would not start from hot without lots of cranking. Even if only left for a minute.

I suspected the special t new style fuel pump check valve (as the similar unit from DMCH has had check valve issues). I installed a brass inline check valve. 
Problem was still there.

Next likely culprit fuel accumulator. One item I had replaced 16 years ago so possible it had failed again. Upon testing it had a slight leak.
New accumulator fitted. 
Problem is still there.

I have found that when the key is turned the first time to position 2 the fuel pump does not prime. Subsequent turning to position 2 always primes the pump. So if I rock the key to position 2 and back to 1, back to 2 and the fuel pump primes and then to position 3 and car starts perfectly.

Anybody have any ideas on the likely fault? Maybe RPM relay?

Many thanks
Nick H

[Chris Williams]

It's an odd one my car does the same (priming) but does not have the hot start issue. I seem to remember chatting with Rich Hutchinson about this once and opinion was varied as to if the cars should prime or not. Sorry I don't have any answer i'm afraid just my observations.
Chris

[Guinney1971]

#2292 never primed on the first go, only on subsequent ones.

In 16yrs ownership, I've never changed my fuel accumulator, but its something we might look at doing
'whilst we're in there' when we finally get time to strip my car down to the chassis as part of the engine
swap and restoration of the chassis, etc.

[Nick H]

Hi Chris/Claire,
Thanks for the info. I picked up a spare rpm relay as it’s a
good idea to have a spare. However I have a theory that it may be the air flow/fuel flap
Position. As I have replaced the metering head. The original unit that was in the car was
A B28F Volvo unit. Now I have a proper refurb DeLorean unit in place. The piston on the
Volvo unit did not have a retainer on it while the new unit unit does.

My thought is the new unit has moved the flap out of adjustment. I am working
away this week so I can’t check it out till I get back on Friday.

Nick H

[Nick H]

Update.

Checked air flow sensor flap position. Looks good to the reference material I found.
Changed RPM relay.

Car starts perfectly from cold.

Car won’t start first turn of key when hot. Second turn it fires right up.
Checked the following while car was hot.

Injectors for leaks.
Disconnect blue plug on CSV. Tried starting, no start.

Swapped blue and grey plugs, car started first turn of key.

Lightly pressed air flow sensor plate and released then tried starting. Car fired up first turn of key.

From this I deduce the car is not flooding but is just not getting fuel. Rest pressure is not enough to fire  the engine hot unless fuel pump is running. 

Car has new accumulator, new check valve and new metering head (so one would assume the O rings in there are all new) and new injectors.
So I’m a bit stumped on what’s causing the problem.

Nick H

[Guinney1971]

Its a DeLorean Nick

[Nick H]

(21 Jul 2018, 21:55)Guinney1971 Wrote: Its a DeLorean Nick  

Tam said something similar   . It has to be said that I may be somewhat of a perfectionist . 
Which probably makes the DeLorean the perfect car, hobby wise as it will never be perfect or finished    



Last thing I’m going to check is the fuel pump by swapping back to original rather than the new style inter-grated pump unit. Moving any further will require a CIS fuel pressure test kit.

That said Dave M’s solid state RPM relay will sort it as it auto primes the pump every time you turn the key.

Pretty sure I had a tank of bad fuel that basicly trashed the injection system. So likely the pump has suffered as well.
Nick H

[TristanC]

I’m sorry I can’t offer assistance Nick - but with the auto prime..... when I turn my ignition to position 2, I hear my pump buzz each time. Is this what you mean?

Tris

[Nick H]

(22 Jul 2018, 08:26)TristanC Wrote: I’m sorry I can’t offer assistance Nick - but with the auto prime..... when I turn my ignition to position 2, I hear my pump buzz each time. Is this what you mean?

Tris

Hi Tris,
          Yes, some cars do and others don’t. In order to have it auto prime each time I would need Dave Mckeen’s solid state RPM relay. As this has auto prime every time as a function of the software.

However my current thinking is the fuel pressure is slightly low.  I have special t’ autos intergrated fuel pump that I fitted a couple of years ago. I kept all the original bits out of the fuel tank so I can easily swap back to standard set up. It’s possible the special t pump has been damaged by bad fuel.

Nick H

[Nick H]

Another update.
Went with my theory that the Special T intergrated pump was only producing just enough pressure when running. In other words it was not enough to sustain rest pressure.
Having kept my original pump and tank components. I temporarily reconnected the old pump and low and behold the hot start problem went away.

Going to go back to the original set up.
I’ll have to replace the fuel pump boot, hoses and the pickup filter. And add a spring to the pick up hose.

Hope this is the end of the saga 

Nick H