AD3/55 fuel pump cold start assist

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ScottUSA
Posts: 19
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

AD3/55 fuel pump cold start assist

Post by ScottUSA » Thu Jul 19, 2018 3:07 pm

The "T" on my 885's cold start screw is broken. It is also stuck fast, it will not turn. Can it be removed from the pump to free it and replace the broken "T" without creating a leak or an adjustment issue? If it is safely removed, what is the procedure? There are two nuts at the screws base that I am afraid to turn until knowing their function.

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db2d
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Location: Monmouthshire

Re: AD3/55 fuel pump cold start assist

Post by db2d » Thu Jul 19, 2018 4:41 pm

The cold start device can safely be removed by undoing the large nut. The unit can then be held in a vice and the smallest nut removed. If the engine is running nominally at the moment the spindle has been over tightened in the ‘off’ position and needs to be turned clockwise to free it. It only takes approximately three quarters of a turn from the ‘off’ position to be fully engaged.
There is a small ball bearing inside that is nipped when the device is engaged, this action locks the injection timing in the retarded position.
New seals are only available for this unit from, davidbrownparts.com They are not included in DPA kits that are freely available elsewhere.

ScottUSA
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Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: AD3/55 fuel pump cold start assist

Post by ScottUSA » Thu Jul 19, 2018 5:01 pm

Thanks dp2d. I have looked at several exploded views of CAV pumps, none showed a cold start. The small ball bearing you reference, is it captive, inside the removed unit? Best to be prepared if it falls free, don't want it to end up on the floor, lost. Here's to hoping the seals survive or can be dimensionally duplicated.

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db2d
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Re: AD3/55 fuel pump cold start assist

Post by db2d » Thu Jul 19, 2018 7:01 pm

The ball is not captive so care must taken. DB are the only ones to have this type of cold starting device. The seals are very small and inexpensive and finding and installing suitable alternatives is extremely difficult. I suggest fitting a new roll pin and turning the spindle clockwise with a pliers type tool before dismantling it.

philedge
Posts: 104
Joined: Sun Dec 03, 2006 11:27 am
Location: Chester UK

Re: AD3/55 fuel pump cold start assist

Post by philedge » Thu Jul 19, 2018 7:59 pm

The T on mine was broken off when I got it and I just used a small punch to knock out the rusted remains of a roll pin that forms the T. Either fit a new roll pin or a split pin and give a good soaking in WD 40 to help freeing off.
'66 880 Selectamatic rat.

ScottUSA
Posts: 19
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: AD3/55 fuel pump cold start assist

Post by ScottUSA » Thu Jul 19, 2018 8:28 pm

I'll give it a soak and try as you both suggest. Last go at it with pliers had me afraid it was going to break. Is it more likely bottomed-out and stuck or has the spindle become bound through disuse and/or corrosion?


dp2d, found the cold start seal kit at DavidBrownParts. I'm trying to find the sense in ordering $3 of parts and having them shipped to the U.S. A voice in my head is saying, "wait until you need something else". Maybe the jaws for my shifter rails (see my other post) are a bargain over there. :lol:

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db2d
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Location: Monmouthshire

Re: AD3/55 fuel pump cold start assist

Post by db2d » Thu Jul 19, 2018 8:56 pm

It has probably ‘bottomed out’ as you say. DB Parts post worldwide every day. I would not be supprised if you spent a lot more money than the postage looking for a seal kit that is not available.

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cobbadog
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Location: beautiful Coopernook NSW. near Taree. NSW. Australia

Re: AD3/55 fuel pump cold start assist

Post by cobbadog » Fri Jul 20, 2018 7:31 am

I have used david brown parts a couple of times for parts and the service and delivery to Australia is the best. Highly recommen them!.

ScottUSA
Posts: 19
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: AD3/55 fuel pump cold start assist

Post by ScottUSA » Fri Jul 20, 2018 12:54 pm

Gave loosening the cold start screw a go last night using vice grips (locking pliers) without luck. Any more effort and I'm afraid somethings going to break. It's off to DB parts for cold start seals and, to make the order worthwhile, a pump seal kit as well. Will have a look to see if they have the transmission shift rail jaws for a reasonable price.

ScottUSA
Posts: 19
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: AD3/55 fuel pump cold start assist

Post by ScottUSA » Fri Jul 20, 2018 7:20 pm

Emailed DBparts but might have lucked-out here at home. May have found a pump guy stateside with the seals. I'm waiting to hear. Thanks for the help.

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db2d
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Re: AD3/55 fuel pump cold start assist

Post by db2d » Fri Jul 20, 2018 10:16 pm

There are many places that have the DPA kits because these pumps are on other engines. These kits do not have the seals for the cold start device because this was only on pumps fitted to David Brown engines. David Brown Parts have the seals for the cold start mechanism manufactured for them by a specialist seal manufacturer.

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mc
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Location: Yorkshire

Re: AD3/55 fuel pump cold start assist

Post by mc » Fri Jul 20, 2018 10:43 pm

The main seal for the cold start is also available on ebay. Search for "David Brown tractor cold start seal"

ScottUSA
Posts: 19
Joined: Mon Mar 26, 2018 1:59 pm
Location: North Carolina

Re: AD3/55 fuel pump cold start assist

Post by ScottUSA » Mon Jul 23, 2018 5:10 pm

I've heard back from Peter Williams @ DBparts. Ran the tractor for a good five hours over the weekend, no smoke at all so I'm thinking the CS must be turned counter clockwise or in the run position. That only means it's okay to run the tractor until the CS is fixed. Given the poor quality of past repairs on this tractor it was a 50-50 chance of which way it had last been turned.

How much does the CS aid in starting a cold engine? I'm hearing DB is the only one to use it and that's why CAV pump schematics don't show one. The tractor is a reluctant cold starter due, I feel to low compression. Runs and starts fine once warm. If the CS is only gives marginal assistance I my leave it be for now.

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ollek
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Re: AD3/55 fuel pump cold start assist

Post by ollek » Mon Jul 23, 2018 6:15 pm

The cold start screw has to be turned out (counter clockwise) for run position and in (clockwise) for start position. The start position has to be selected before the starter motor is putted into operation and the screw has to be screwed out right after the engine has started. The engine will run roughly and smoke when you increase the rews, if the screw is in the start position (screwed in). The screw is a mechanical lock for the automatic injection timing advancing system in the pump. The screw will, when screwed in, keep the injection timing retarded, making it easier for the starter motor to get to the needed rews for starting the engine.

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rid54
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Location: Vallentuna, Sweden

Re: AD3/55 fuel pump cold start assist

Post by rid54 » Mon Jul 23, 2018 6:34 pm

Text edited due to my not properly reading an earlier post...

My tractor (an 880 Selectamatic) has the cold start screw blocked just as yours. In winter, I use the thermostart, which allows quick starting from cold, even when the temp is well beolw freezing point. In more clement weather (+5C and higher), the engine starts without either of these systems in use.

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