HPCA and Fast Idle Control

[johncarrol]

I replaced the 6.2 NA with a 6.5 NA in my 1991 GMC. The HPCA and fast idle control system on the 6.2 always worked fine. When switching over the coolant temp switch from and to the rear corner of the right/passenger head on the engines, I noticed one of the blades was loose and I decided to replace the switch. I went to Autozone and what they looked up for my truck did not fit my connector. It was a 2 pin switch that used a different pigtail. I told them I believe my truck came from the factory with the switch I had. We looked at switches for other year trucks with 6.2s and came up with a photo of one that was very simular to mine for an older 6.2. I had it ordered, but when it came in, the thread size was bigger. I returned it and decided to go to NAPA and see if they had anything different. All they had for a 1991 was the same thing as Autozone except they sold the correct pigtail separately. I figured the older switch was replaced by this new one which had the same thread size, so I purchased it and its pigtail. Now things get interesting. Before installing it, I decided to get my ohm meter out and check it against my old switch. I checked my old switch at room temperature which gave me a closed circuit through it. then I put the end in a pan of water and checked the reading while heating it. The circuit opened around 100 degrees. This made sense to me. then I tried this with the new switch, but its circuit stayed open from below room temperature up to boiling temperature. I returned the switch. They brought out 5 more switches to the counter and all of them had open circuits at room temperature. I went back to Autozone and they looked up and found another switch with a yet a different connection but same thread size for a 1990 that was called a glow plug control temperature switch. It had a closed circuit at room temperature, but when I heated it at home, the circuit never opened while heating it up to boiling temperature. Until I get a reply as to what the heck is going on or I'm doing wrong, I cut the wires and installed a toggle switch between them to activate my HPCA and fast idle during a cold start and for a few minutes after. What baffles me is: if all the new switches I checked against my old one are not bad, then what are they good for? You would think they are supposed to monitor coolant temperature and react to it in some way? I attached a photo of my origional switch.

[john8662]

I think that part is pretty much a dealer item.

I've replaced a few just always gotten one at the GM Dealer.

Same switch from 82 through 93, just gets to mount in different places in later years.

[More Power]

1982-93 Fast-Idle/HPCA switch, 95 degrees GM PN-10154649

Jim

[NH2112]

Ford p/n E8TZ9E939A may work, it's the temp switch for a 6.9l/7.3l IDI. 1/2" NPT, I believe. I'm pretty sure the hex is 13/16", which is definitely too small for 3/4" NPT.

http://item.mobileweb.ebay.com/viewitem?itemId=230849228280

[johncarrol]

Thanks guys, GM was my last option. My local GM dealer is kind of a pain in the butt when I go to the parts dept. asking them to look up something older without knowing a part#. Giving them a part# will make it much easier. While I'm thinking about it, Two unrelated questions: Does the part that sits on top the oil pump drive mechanism at the top rear of the engine block with the 2 wire plug hooked to it, send a signal to the electric lift pump circuit? What does the plunger on the gear end of the IP do?

[Robyn]

GM is the only real shot for this switch.

The switch should be closed at room temps on down and open at around 100f as mentioned.

Some rigs had another switch mounted on the rear of the RH head at the top side, that controlled the glow plug inhibit, which simply kept the glow plugs from cycling when the engine was warm (idea was to save the plugs) this was fine until the switch died and left you dead on a cold morning.


Get the GM switch and your good to go.


Missy

[More Power]

Does the part that sits on top the oil pump drive mechanism at the top rear of the engine block with the 2 wire plug hooked to it, send a signal to the electric lift pump circuit? What does the plunger on the gear end of the IP do?

The 2-wire connector on top of the oil pump drive is the output for an engine speed sensor. In the 80's 6.2 rigs, it was used as an input for the emissions control computer (probably CA models). In later years, it was also used by the TCM (transmission control module) in conjunction with either a 4L60-E or 4L80-E automatic.

For those who convert their electronic 6.5 to mechanical fuel injection, they need to acquire such an oil pump drive to allow interfacing an aftermarket TCM.

The plunger on the end of the injection pump shaft pre-loads the shaft rearward. I suppose this helps prevent the head and rotor from moving front/rear, and may help it live longer or work better.... I dunno... Jim

[johncarrol]

Thanks again. Had a switch ordered yesterday. Wow! $70 + tax.

[DmaxMaverick]

70 Bucks? WOW! Is it too late to cancel?

http://www.amazon.com/ACDelco-10154649-Switch-Assembly/dp/B000C9D1SW/ref=sr_1_1?ie=UTF8&qid=1364647984&sr=8-1&keywords=10154649 (http://www.amazon.com/ACDelco-10154649-Switch-Assembly/dp/B000C9D1SW/ref=sr_1_1?ie=UTF8&qid=1364647984&sr=8-1&keywords=10154649)

$18.92, and it ships free, if you can manage to spend $25.

Just a note, the thread is 3/8-18.

[johncarrol]

I didn't want to sound like a cheapskate, but that's the real reason GM was my last resort. I believe, as others do: 'That switch shouldn't cost more than about 20 bucks." Any other time a part is usually on back order, but as my luck goes, they have it in waiting for me. Thanks for giving me an alternative place to look. I'll remember to look in Amazon in the future.

[DmaxMaverick]

Nothing wrong with being a cheapskate. Most of are, to some degree. Money doesn't come easy to most, and 50 bucks is 50 bucks. I don't owe anything to GM. If I can't get their parts dept. to wholesale (at most) a part to me, I get it somewhere else. The only exception is emergencies, when they have the part in stock. In almost every case, I can get a part delivered to my door before they can to theirs, at a fraction of the cost. Unfortunately, the dealer will make up for my cheapskate-ness through you.

Anymore, Amazon is one of the first places I look, for nearly anything. You'd be surprised what they have available. It used to be just books. Ebay is another good source, as long as you deal with reputable sellers and new/unique products. I rarely ever engage in the auctions, but have for some items not available anywhere else reasonable.

[johncarrol]

I told my friend about the availability of some new GM AC Delco parts on Amazon I learned from you good people here. He wondered if Amazon or anyone else had access to Delco batterys. He believes Delco batterys are the best out there. I haven't owned a GM purchased new in such a long time, I forgot how good Delco batterys are. :)

[DmaxMaverick]

Batteries are a tough one. It's best to find a local distributor and work out the best deal. Buying individual batteries from online outlets is usually cost prohibitive, as the shipping is very high. Distributors pay freight on a truckload, which really reduces the individual cost.

O'Reilly's carries Delco batteries.