Windshield Wiper Troubleshooting

Hi all, I recently acquired a 76 XJ6 for my wife, and it has a few little issues. For the curious they are: a tap from the exhaust side valve cover, but only at idle (the stakedown kit is on its way but the only at idle concerns me), poor cold starts, a bit of run on, and the wipers don’t move at all. I’m fairly confident I can handle the rest of the issues without help, but I’d love some help figuring out these wipers. The fuse is good, and when I switch them on there’s a pretty definite click from the relay near the glove box. Should I assume motor problems? Wouldn’t that be blowing the fuse?

Get the schematics.
Check that you get the correct voltages at the windshield’s motor plug at the corresponding switch positions.
Connect the motor to a 12v power source and see if it works.
It will give you an idea of what’s wrong.

Once you have them working, installing relays is highly recommended.

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You need to check valve clearances, Jake - and there is also the possibility that the tapping may just be a wandering adjustment shim. Removing the cam covers for this operation will also clarify if the tapping is caused by a wandering tappet guide - requiring the stakedown.

As to the difficult starting and the run-on; I assume you have cars? Carb adjustments may cause run-on, and a faulty AED both that and difficult starting…

There is no relay specifically for the wiper motor - it is powered from the ignition protection relay. Which ‘clicks’ when ign is turnoed ‘on’. However, there is a relay involved if intermittent wipers are installed - which may click when wipers are turned on.

Aristides’ advice is highly relevant; a wiring diagram is pertinent for testing - the wiring is somewhat intricate. However; in ‘fast’, you should have power on white/light green - and 'slow, on black/light green. As a starting point, but the switch is also used to change motor’s and ground connections - and without ground the motor won’t run…

Frank
xj6 85 Sov Europe (UK/NZ)
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I have the Leyland factory repair manual which is Great for the physical steps of disassembly but as far as I can find only has a master wiring schematic, not specific ones for each system. I do not have intermittent wipers but there is a definitive relay clock from near the glove box when I turn them on and off.

Thank you for the advice on all topics. Yes, I’ve tuned quite a few carbs, but only of the standard American persuasion. I’ve been doing my research on these. I don’t have an AED because I have the Zenith Stromberg carbs. I suspect my bowls are losing their prime somehow. I’ll also be investigating the anti run on valve as an obvious run on candidate. On my theme of being more familiar with American cars, I’ve never checked valve clearance on an overhead cam, just rocker arms. I’ll research that. I am familiar with the idea that metal wafers are involved in correcting the clearance. You think one of those may be on the loose? I’m taking the valve cover off this weekend, tomorrow in fact, to install my stakedown kit. Even if that’s not the problem, my understanding is that it’s practically a required insurance for the XK

Checking is very easy, when the lobe is pointing away from the tappet, slide in a feeler gauge and write down the largest that will fit. #6 cylinder is the one at the front.

The cam pushes on a bucket (the one you see) called tappet. The tappet runs in a guide, the tappet guide, these can creep up until the cam hits them and eventually smashes them to pieces.
Between the tappet and the valve stem there is the little shim that adjusts the clearance. If you need to exchange them, you have to release the upper timing chain tension via the breather cap and then remove the camshafts, pull out the tappet with a magnet and change the shim, then put it all back together and see if you got it to spec.

The hold downs are recommended, yes. Especially on the fuel injected cars, but it can happen on all.

Hello Jake - I had a condition of my wipers operating slowly, and then they stopped working - this is on my 1991 XJS V12 Classic Coupe - I removed the wiper motor mounting section grille, then unplugged the wiper motor harness from the bulkhead connector, so I could check for power and ground conditions - when I unplugged the connector, I found that there was corrosion on the pins of the connector - I cleaned the pins and found that my wipers are now working correctly - go to the XJS section of this Jag-Lovers forum, and search for “windscreen wiper motor bulkhead connector” and you will see the post with the photos of the corrosion condition - hope this helps you - Tex Terry, II - 1991 XJS V12 Classic Coupe, 1986 XJS V12 Coupe - sent 7/24/2020 1324hrs. EDT USA.

I found your post, I’ll keep that in mind as a possibility as I probe connections! I was surprised to see that there even was such an intermediary connection like that. I usually but I suppose I see the purpose.

That procedure sounds rather involved! Here’s to hoping they spec out right. There definitely is a tick. I’m kind of HOPING to find wear on one of the tappet guides because that’s arguably the easiest engine tick to fix.

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The adjusting shims is fitted between the valve stems and tappet, Jake - and an uneven shim may cause 'tapping). This is usually intermittent, and basically audible only in idle…

Since your tapping is on the exhaust side; a wandering tappet guide is the more likely cause - and a stake-down kit will easily remedy that. Unless there is serious damage to a tappet guide…

As an aside; ‘checking’ valve clearances is straight forward - adjusting them is not…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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Frank
xj6 85 Sov Europe (UK/NZ)
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