1800: P1800ES fuel injection

[VolvoRoyS]

Originally Posted by 142 Guy

The advance values (RPM and degrees) for the centrifugal advance mechanism provided in the 1971 Volvo Service manual are specified as degrees and RPM in the distributor. Because of the 2:1 timing gear ratio the advance angle at the crankshaft is twice the advance angle at the distributor. That is why I multiply the distributor advance values by 2 when adding to the static advance value to get total advance measured at the crankshaft.

Well I've learnt something there. I don't think I have ever come across distributor advance degrees before; it's always been advance at the crankshaft pulley that I have seen. I knew that the distributor rotated at half engine speed. Later on in the green Volvo manual it gives some information on setting the timing with a strobe and there talks about 10deg BTDC, so is now talking crankshaft speed, but I can see no mention of where to find the 10deg BTDC mark. At least the Haynes manual has a diagram of the crankshaft pulley but I have to say I had a hard job finding the marks.

Anyhow, what I taking from this is that 5 deg (in addition to the 10 deg BTDC static timing ) that I'm getting at the crankshaft pulley is equivalent to 2.5 deg distributor advance, when in fact I should be getting zero advance as no advance should occur before 375-550 (dist.) or 750-1100 crankshaft. So need to retard the ignition slightly. In fact I'm closer than I thought as advance could begin at 750 crankshaft speed; needs just a little tweak.

Might do that tomorrow. Many thanks again for your input,

Roy

[142 Guy]

Centrifugal advance mechanisms are not exactly precise devices. They have a couple of weights that move outward as the distributor speed increases. As the weights move out they rotate the plate on which the contacts are mounted creating advance As the distributor slows down there are a couple of springs that pull the weights back in which reduces the advance. If the springs get old or you get grunge in the pivots for the weights or on the actual plate on which the contacts are mounted the assembly is not free to rotate. You might have a lump of dried dirt / grease / oil which is preventing the advance mechanism from returning to its no advance position at 750 RPM.

If the advance mechanism has never been cleaned and lubricated you might want to try that before checking the timing.

[VolvoRoyS]

Originally Posted by 142 Guy

Centrifugal advance mechanisms are not exactly precise devices. As the distributor slows down there are a couple of springs that pull the weights back in which reduces the advance. If the springs get old or you get grunge in the pivots for the weights or on the actual plate on which the contacts are mounted the assembly is not free to rotate.

Well that would explain why having set the static advance to 10 deg. BTDC the dynamic advance was slightly different. For now I've retarded the ignition slightly and am now getting 10 deg. advance on the strobe. I've also fitted a replacement spark plug of type BP6HS provided free of charge by Brookhouse. I did notice that on the old plug that I removed I'm now getting some light brown deposit on the plug tip which to me suggests the mixture can't be far out. And the engine remains responsive to the throttle with an idle speed of around 800 RPM, but still with slight hunting.

I feel I need to drive it now and see how it settles down. I needed the car running properly to trouble shoot the vibration I'm getting. I hoping that is the prop shaft.

Roy

[VolvoRoyS]

Started the car up for the first time this year at the weekend. With The TTS now working the engine fired and ran after a couple of seconds. The engine idles at about 1800 rpm at first then drops abruptly to around 1000 rpm and then starts to fluctuate wildly and eventually stall. I can keep it running by giving it some throttle and eventually when warm it will idle steadily around 700 rpm. It's done this since I first got the car and I now realise that it is similar behaviour to another car that I have that has an Auxiliary Air Valve (AAV). I fixed that by replacing the AAV. So I suspected the AAV.
Looking on the internet I found this video which showed very similar behaviour. This is on a Mercedes but it has D-Jetronic fuel injection and has a similar AAV. Here is a link to the video:
https://www.youtube.com/watch?v=_TCd_bHKWTA

So I decided to remove the AAV and test it. I have found that if I put it in the freezer it opens fully and if I put it in hot water it will close but only above 70 degC will it close fully ( it should close fully at around 60degC). I have used carb cleaner to attempt to clean it in the same way as the video but without taking it apart. Looks quite clean but suspect that since I can hear a gentle clicking noise as it opens and closes that there is still some friction present. So now thinking of lubricating it with engine oil. Has anyone any suggestions as to the best lubricant to use?

Roy

[JP 1800]

I have seen this numerous times with d-jet systems, some of the wax may have leaked out of the AAV thus a higher temp may be necessary to fully close, also check the tightness of the hoses attached to the aav as you may also get an air leak there. The reason for the high revs then sudden drop is due to the "coasting" feature thats designed to shut off the injectors when the throttle is in the closed position when the revs are over a fixed rpm. Due to an air leak the revs jump up, however because the throttle switch is closed the ecu thinks the car is coasting and cuts off the fuel until the revs drop to idle speed and then opens the injectors again. With the injectors open again the car can rev up and the cycle happens again. This will go on and on until the car eventually cuts out.

[JP 1800]

Also to add, some individuals slightly crimp the bulb to compensate for the lost wax, however this is a risky mod as you may damage the bulb causing a puncture leading to all the wax leaking out. Regarding lubricant, you can try atf and acetone mix as this may be thin enough to go between the piston and the housing. The sticking is caused by galvanic corrosion as the housing is alloy.

[cassell]

Originally Posted by VolvoRoyS

Started the car up for the first time this year at the weekend. With The TTS now working the engine fired and ran after a couple of seconds. The engine idles at about 1800 rpm at first then drops abruptly to around 1000 rpm and then starts to fluctuate wildly and eventually stall. I can keep it running by giving it some throttle and eventually when warm it will idle steadily around 700 rpm. It's done this since I first got the car and I now realise that it is similar behaviour to another car that I have that has an Auxiliary Air Valve (AAV). I fixed that by replacing the AAV. So I suspected the AAV.
Looking on the internet I found this video which showed very similar behaviour. This is on a Mercedes but it has D-Jetronic fuel injection and has a similar AAV. Here is a link to the video:
https://www.youtube.com/watch?v=_TCd_bHKWTA

So I decided to remove the AAV and test it. I have found that if I put it in the freezer it opens fully and if I put it in hot water it will close but only above 70 degC will it close fully ( it should close fully at around 60degC). I have used carb cleaner to attempt to clean it in the same way as the video but without taking it apart. Looks quite clean but suspect that since I can hear a gentle clicking noise as it opens and closes that there is still some friction present. So now thinking of lubricating it with engine oil. Has anyone any suggestions as to the best lubricant to use?

Roy

Roy,

I've been through exactly this issue with my own ES and as a temporary fix until I could source and afford a replacement AAV I created a 'manual choke' arrangement to aid cold starting and acceptable tickover.

It works so well that I've left it in place and actually published the attached summary in Driver magazine so that other owners could copy, I understand that several including some in USA have created similar set ups. It's a cheap fix and actually looks quite professional under the bonnet!

I've just had an engine rebuild completed on my ES and managed to find a good working AAV which has been fitted. I will however be keeping my manual choke bits handy for when, and if, the AAV fails again.

I attach a PDF document for your interest, good luck.

Paul

[VolvoRoyS]

[QUOTE=JP 1800;2885904Regarding lubricant, you can try atf and acetone mix as this may be thin enough to go between the piston and the housing. The sticking is caused by galvanic corrosion as the housing is alloy.[/QUOTE]

By atf do you mean Automatic Transmission Fluid? I don't have any of that but I do have some Power Steering Fluid which, I think, is very similar. The guy in the video uses WD40 which I believe can leave a residue which might make the sticking worse in the long run.

Roy

[VolvoRoyS]

Originally Posted by cassell

Roy,

I've been through exactly this issue with my own ES and as a temporary fix until I could source and afford a replacement AAV I created a 'manual choke' arrangement to aid cold starting and acceptable tick over.


Paul

Interesting idea. I'm hoping a bit of lubricant will fix mine. I have just received a couple of gaskets from Brookhouse (I bought two as I expect to be taking the AAV on and off a few times) and a new hose for the air filter side as the old one is dirty and may have deposited dust into the AAV, particularly as the air hose from the air filter was torn so would have been getting unfiltered air.

Roy

[JP 1800]

Originally Posted by VolvoRoyS

By atf do you mean Automatic Transmission Fluid? I don't have any of that but I do have some Power Steering Fluid which, I think, is very similar. The guy in the video uses WD40 which I believe can leave a residue which might make the sticking worse in the long run.

Roy

Hi Roy, yes I am refering to automatic transmission fluid, it needs to be thin enough to seep into the crevices. The AAVs can be stripped down but this can be difficult due to the corrosion.