Hey guys! I’ve got a 1990 Daimler double six that’s recently becoming hard to start when cold. Only when cold. It starts fine every time when warm.

what I’ve done/checked so far:

-AAV: cleaned and tested, it is opening and closing when it should

-Throttle body(s) set to 0.05mm adjusted throttle linkages.

-New fuel pump and all new injectors/pipes.

-New distributor and HT leads (I haven’t changed the plugs yet but am going to do very soon)

The AAV is defiantly working but it does not seem to affect the rpms at all!? Cold engine or warm the rpms are always around 700.

The car runs and drives just fine, just hard to start when cold, sometimes I have to hold the throttle for 20-30 seconds before it will idle without cutting out.

Any tips will be appreciated.

 

Just to clarify, is it a cold starting problem or a cold running problem? Or both?

The "could be" list might get long.

The CTS (Coolant Temp Sensor) is one possible culprit as it plays a major role in cold fueling and cause problems in both cold starting and cold running. About $20 and 15 minutes to replace so, as guess go, it is fairly painless. However, if you have an ohm meter your CTS can be tested; we have the specs

Cheers
DD

Cheers
DD

 

How did you test the AAV? The revs not changing is a classic sign of the piston inside the AAV being stuck.

If you give the car some throttle and then crank from cold will it start?

 

Hi! It’s a cold starting/ cold running problem. Sometimes
i have to hold the gas pedal for around 20-30 seconds before it will run and idle on its own. Other times it will start up normally. But it’s getting worse. Once it’s warmed up abit it starts and runs completely fine.

about the CTS I noticed that the temperature gauge in the car reads about 10 degrees higher than the actual temp (tested temps with a IR laser thermometer)

 

After looking at images online of the AAV and comparing with mine, it looks to be fully open when cold, if I place the bottom (bulb) in water of 80 degrees C’ I see the piston start moving down (closing)

 

I am still not clear.
Once you turn the key to start, how long before it fires? Not fires and runs on its own, just fires the first time, even if it does not catch?

 

ah sorry. Well, it will crank for roughly 10 seconds, fire for literally a second or two then die. Crank again for another 10 or so seconds, and the same. It will only fire if I press on the gas pedal just as it catches. I then have to hold the gas pedal for about 20 seconds before it will run on its own.

it does not always do this, sometimes it will crank for 10-15 seconds start and run rough on its own for about 30 seconds or so then it smooths out and runs nicely.

Once warm it pretty much fires right up without problem.

 

Mmmmm,

AAV sounds hissy, my repair PDF is attached, with snaps. The piston moves UP as the wax pushed the pin out.

Spark plugs on a HE are a PITA for a cold start/run engine. Do them, then move to other items carefully.

The CTS has NOTHING to do with the gauge. The ECU CTS is a 2 wire Sensor at the backside of the B Bank stat housing. The gauge Sender, is a 1 wire at the backside of the A Bank stat housing. They DO NOT talk to each other.

One of mine, a PreHE, is a PAIN, and I usually prime the rail with 2 or 3 "ons" of the ignition switch, leaving the last "on" as ON, then push the gas pedal to the floor and back ONCE, and it starts and runs every time. That single Down and Up with the Ign ON, triggers a squirt of fuel from the Injectors, like a carby Accel Pump.

BUT

All this is of no use if the answer to Gregs question is NO. If its NOT coughing and farting, as in trying to "catch" at cold cranking the plugs are #1 on my list. If that coughing etc is happening, but it fails to "catch", still pugs @ #1, but AAV slips in there also, along the list Doug mentioned.

 

I sugest, in this order:

1. new plugs gapped to 25 thou,
2. new HT leads, rotor and dizzy cap
3. clean the resistor pack connector very carefully and thoroughly see this. Assuming none of these items have been recently renewed, this is just maintenance that should be done anyway. link to resistor pack servicing procedure: https://www.jaguarforums.com/forum/x...sistor-134745/
4. Then try a cold start
5. If nothing, or not really right, then replace the B bank fuel pressure regulator, as this might well be the true underlying problem.

 

With ignition ON, you get the 1 second fuel pump priming burst.

Try ignition ON prime 5 times before crank.

If things improve there could be a pressure issue: a regulator as Greg says, or the on-way valves allowing bleed down.

Rob

 

hello! I primed the rail 3 times, on the third time I left the ignition on, pressed the pedal to the floor once. Turned the key to start and it fired up almost immediately.

 

Good. You are narrowing down the problem. It looks like a fueling problem, not an igntion problem.

You can break this down evern further. Next cold start eliminate the the pedal push but prime the rail as you described. If the engine starts well then it suggests you have a fuel pressure problem: weak pump or fuel drain-back perhaps.

Now try a cold start with just the pedal push. If the engine starts easily with this manually induced extra fuel it suggests that the rail pressure is OK and a faulty CTS or some other fault where the system is not richening the mixture for cold starting.

Cheers
DD

 

An update

I changed all the plugs, now the car starts fine every time except now the idle is at 1000rpm when warm? Why would new plugs cause a high idle condition? In gear it’s around 650rpm

 

Nothing really.

BUT

To do the plugs a LOT of stuff is pushed and pulled around for access.
A vac hose dislodged is the #1 culprit, usually.

OR

Someone has adjusted the AAV HOT idle screw to mask other things, and now needs resetting as described it that write up from earlier.

 

well the cold start issue turns out to not be resolved. Back to the same problem again. And now it keeps almost stilling every now and then while driving

 

As for the cold start issue....don't pull any more hair out until you've replaced the CTS. It'll be the easiest thing you've done and there's a halfway decent chance it'll solve the problem.

Stalling. This developed only after replacing the spark plugs? If so, carefully trace back all your work. When working on these engines is is very easy to inadvertatnly jostle something loose or compromise some engine-baked hoses or wires.

Cheers
DD