1800: Cold Start Weirdness

[Derek UK]

Valve looks like this one so appears to be the right way round, but still worth checking.
https://www.7ent.com/products/check-...o-17h2646.html

[142 Guy]

Originally Posted by LawsonJD

First things first have we got the various manifold pipes on right?
Left to right, to oil filer cap, to servo, to crankcase breather.
I'm not actually there and these are V low res.

What year / engine is this? The oil filler cap and brake servo connections are correct. The crankcase breather (going to the little box on the left side of the engine?) looks odd; but, probably OK. On the D jet engines up to 1972 (at least on the 140) the hose from the crankcase breather ran into the bottom (filtered side) of the air filter. My D jet does not have that nipple on the far right at the inlet. As long as that port is well in front of the throttle plate then it is close to atmospheric pressure and will work for the filtered air inlet to the crankcase. Perhaps that nipple is an 1800 feature or a late production change.

I presume that copper line to the port on the top of the manifold at the inlet is the line to the distributor? If so, that is correct. Unusual; but, correct.

Check to make sure the nipples on the line to the oil filler cap and the brake servo are correct. The nipple for the oil filler cap will have a small restricting orifice inside. The brake servo nipple will have a large unrestricted opening.

[LawsonJD]

It's a 1971 B20E, I do know that the North American intake manifold differed from the Euro ones in the crankcase breather return connection.
I don't know what that wire is I'll ask tomorrow.
Tried clamping the servo hose, no change.
I'm going to pursue your other suggestions guys but it'll probably be next week.
I've got a spare ECU as well so might swap that out.
Thanks very much so far.
David.

[142 Guy]

Originally Posted by LawsonJD

It's a 1971 B20E, I do know that the North American intake manifold differed from the Euro ones in the crankcase breather return connection.
I don't know what that wire is I'll ask tomorrow.
Tried clamping the servo hose, no change.
I'm going to pursue your other suggestions guys but it'll probably be next week.
I've got a spare ECU as well so might swap that out.
Thanks very much so far.
David.

That is interesting. A little investigation shows that the fitting on the intake manifold appears to be an 1800 feature. The 140 has a large filter housing with a convenient spot designed into the bottom for the crankcase air inlet. The 1800 being a tighter fit may not have had room to accommodate the connection to the filter housing so it got the extra fitting on the manifold. I have a friend with a 1970 1800 E; but, I guess I wasn't paying attention to that particular detail.

Technically, that nipple at the front of the intake manifold is not the return connection. It is the fresh air supply to the crankcase and the crankcase fumes exit from the oil filler cap and are sucked into the intake manifold at that fitting in the center of the intake manifold. Inlet and outlet are a little bit academic because Volvo has switched the direction of flow over the years.

When you clamped the servo hose and you got no change, does that mean that when you pressed the brake pedal when idling the idle still became erratic or does that mean there was no change in the idle when you pressed the brake pedal. If it means no change in the idle with the hose clamped, I think that means that you have identified the source of the idle problem???

I would be dis inclined to fiddle with the D jet controller. If the engine runs and is driveable when hot then I think that means the controller is just fine. The controller tends to be about the least problematic part of the D jet system.

[VolvoRoyS]

Originally Posted by LawsonJD

Tried clamping the servo hose, no change.

David.

I had a wildly fluctuating idle on my 1973 1800ES during warm up which turned out to be the AAV sticking. Has the part been checked? I don't think new ones are available so it is likely that the old one is being used. It looks like you have eliminated the servo so could be the AAV

Roy

[LawsonJD]

That's what I beginning to think, that the AAV has taken the pip. and that's from speaking to my guy and reading the Dr D Jet page.
I'm going to go through the guy's fault diagnosis suggestions steps first though then we'll see.
This one was rebuilt by Brookhouse in 2013 which does make me reluctant to spend my way out of this.
If it is the AAV Skandix do an electrical conversion kit for about £200.
Out of stock at the moment.

[142 Guy]

Checking the AAV is pretty easy. Pull off the top robber hose on the AAV so that you can look down into it. You will see a notched Vee. When the engine is cold that Vee is open and admits additional idle air. When the engine is hot the Vee is completely closed off. If it stays open or closed regardless of the temperature - its bunged. Sometimes a liberal dose of penetrating oil will free the valve up as long as the thermostatic element has not failed. With regular application of lubricant my original 1971 AAV was still working in 2016 when I pre-emptively removed it and replaced it with a more modern / cheaper / easily available PWM idle valve from a B230 FT.

That Skandix retrofit kit is a nice alternative. However, I think it may have become permanently on back order. The kit uses the AAV from the later K jet fuel injection system and the K jet (in its pure mechanical form) has been out of production since the early '80s. It would not be unreasonable that OEM K jet AAVs have also followed the system into oblivion. I think the Volvo part number for the K jet AAV is 1269319 and it comes up as discontinued at most places. If you can find one you might want to snap it up because you can always fabricate the rest of the bits on your own to make an idle control system. Skandix also has this thing for a breathtaking price

https://www.skandix.de/en/spare-part...valve/1022926/

For that price you can definitely retrofit a later PWM idle air valve from a 700 / 900 series Volvo with a small one board controller and have money left over for one or two cases of a nice Chilean Cabernet.

Your AAV might be a problem; but, a stuck AAV will not cause the idle hunting / oscillation problem directly. A stuck AAV will leave you with a really low / no idle when cold or a really high idle when hot. The idle stability occurs when owners find they cannot work around the high / low idle because they hit the limits with the normal idle by-pass screw and then try to fiddle with the throttle stop screw to adjust the air flow using the throttle plate which then screws up the idle control switch in the TPS which cause the idle stability problem.

[LawsonJD]

So testing the AAV, when the brass bulb end is hot, say in a cup of boiling water, there should be an airtight seal between the 2 air pipes, is that right?
I'm going to go over probably Thursday next week and we're going to work this problem in a methodical manner including penetrating oil.
By the way Bosch don't refurbish these, I asked when I got my MPS overhauled.
Thanks very much guys as usual.
David.

[volvobysea]

Hi David

There was a thread posted on here titled EFI intake plumbing a few years ago that detailed the repair of an AAV and having done this myself it was fairly easy to follow the steps.

In this thread there was also a mechanical replacement of the AAV. I also fitted this for a while and it was like operating a choke to supply the extra air needed when cold. The only issue I had with the mechanical system was some backlash. The backlash could have been corrected with a suitable return spring. I resorted to just manually resetting the system after the cold start.
I now have put my AAV back on having reconditioned it. I always had cold starting problems for years as mine was stuck fully closed. Now the car behaves as it should idling at about 1500 RPM until the AAV fully shuts when warm.

Thread Link

https://www.volvoforums.org.uk/showt...lumbing&page=2

I hope this helps

Gavin

[VolvoRoyS]

Originally Posted by LawsonJD

So testing the AAV, when the brass bulb end is hot, say in a cup of boiling water, there should be an airtight seal between the 2 air pipes, is that right?

David.

To test the AAV I removed it from the car and first put it in the freezer for a couple of hours. Then allowed it to warm up to room temperature before putting the brass bulb part in hot water. I found that it would open fully only at 70 deg C but this seems good enough. I think I cleaned it first with copious amounts of carb cleaner, after it came out of the freezer, so fully open, and again after it was fully closed. Repeated this a few times.

Roy