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Cold Start Injector leaking



My cold start injector is leaking. If I shut down with the engine warm and let it set for more than 10 minutes, then it will only start if I use 1/4 throttle and I get a ugly puff of black smoke. If I restart before 10 minutes it fires right up.

I've replaced my main injectors with new ones, replaced all of the valves, springs and seals when I pocket ported the heads, so I don't think its the main injectors or oil smoke. I asked my local Chevy dealer to search for a new cold start injector, but he found that they are no longer serviced.

Anyone have a source for a new one, or know if they can be repaired?

I've put a lot of money into my engine and it's really embarassing to start up blowing smoke in public! :eek:
I've been looking since I first saw this question, but haven't found anything yet. Hang in there Dennis. ;)

_ken :w

Thanks for the help!

I just finished reading about your engine project - AWSOME :dance

CAC is an incredible site! :cool

Wish I'd been here a long time ago - keep up the good work!

I still haven't located a source to buy them, but I found some reading for you in the meantime (just in case you didn't already know it ;)).
Since cold starting requires considerably more fuel than a warm engine, it must have some means of enrichening the fuel to air ratio until the temperature of the engine rises to where the fuel will vaporize more readily. The choke systems restricted the air intake so that there was less air moving thru the carburetor while at the same time opening the throttle plate below the choke plate and drawing more fuel. This causes a rich fuel mixture that will enable the engine to run.

The cold start injector (or valve) is mounted in the intake manifold at a centrally located area where it can open and allow extra fuel to enter the engine. This is in addition to the normal fuel injection system. The extra cold start injector is electronically controlled by the computer (ECM) and when the temperature sending units signal the computer that the engine is cold, the computer will send a signal to the cold start injector to inject fuel at the same time as the normal injection system. This makes the air fuel mixture richer to compensate for the cold engine requirements.

The cold start injector delivers fuel to all the cylinders and is controlled by a thermo switch and time control. Thermo switches are located in an area in the engine where engine temperatures can be sensed such as the coolant or head temperature. The temperature sensor has the ability to open the switch when the engine is warm enough to run on the regular injection system or close when the engine is cold and needs more fuel. It activates the cold start injector until the temperature deactivates the thermo switch. (The temperature rating on the switches can be checked in shop manuals).

Whether the sensor is controlling the cold start injector long enough can be felt by cold engine hesitations after the vehicle has run for a few minutes and prior to normal engine temperature. If the temperature sensor rating is too high or staying on too long, there can be some flooding or black tailpipe smoke generated for awhile at about normal engine temperature and also lower gas mileage. It is critical that the correct temperature sensors are used so as not to overload the catalytic convertors and foul the oxygen sensors or cause the cold start injectors to work improperly.

HOW TO TEST A COLD START INJECTOR -- when the cold start injector is in a hard to reach area, a pressure drop test with the injector in place can be made. A pressure gauge can be installed at the fuel filter location (as illustrated in the fuel injection cleaning system by Airtex) or at the fuel rail connector. The fuel system can be pressurized by momentarily by-passing the fuel pump relay and then connecting an injector activator to the cold start injector to energize it. This will cause a pressure drop on the gauge if the injector is working. It can also be tested to see if up and then activating the cold start injector. The engine should falter or miss when this is done and possibly black smoke appear from the tailpipe due to the excessively rich mixture.

When the cold start injector is easy to get to and can be removed easily, it may be removed and activated in a container to check the fuel spray pattern. This will enable the injector to be cleaned with a commercial spray cleaner if desired when the spray pattern is not conical or when the injector drips while pressurized.

Loss of electrical power could also be a reason for the cold start injector not working. This can be checked by disabling the engine so it won't start and then connect a test light into the cold start injector connector. The test light should stay on for a short duration when the ignition is turned on. A stop watch can be used to measure the duration of the light staying on. Shop manuals will tell how long each duration of activated injector time is required. The above test should be performed on an engine that is cooled off and prior to start up in order for the injector to work in the time established for proper performance.

Winterizing your vehicle is still a wise precaution, but it now requires a different technique due to fuel injection. The cold start injector has replaced the old choke problems and will make for a better performing engine if certain precautions are taken to assure that it is working properly.

I'm still lookin'! :gap
The cold start is no longer available. What I would recommend doing to PROVE it's the cold start injector is, put a fuel pressure test gauge on the fuel rail. Do this with the car at operating temperature. Start the car and let it idle and note the fuel pressure, shut car off and see if the pressure leaks down. If it leaks down to zero within 5-10 minutes than it is a leaky injector. If it holds pressure the injector is not leaking.

Have you tried disconnecting the cold start sensor at the front of the intake? This could be bad also causing it to add fuel even though it is not cold.

If it proves to be bad, I would get a block off kit, Accel has these, they are about $40 and they block the injector hole and the fuel rail hole. Than you will need a 89 chip which was the first year without coldstart and the last year with MAF. Or have a custom chip made with a 89 cold start table.
This is great information on the cold start injector. I seem to be having problems when the cold start injector shuts off, do you have any more info? Like how the car sets the idle, after the cold start injector is shut off.
Thanks Tom,
Oops! :eek:

Usually, if you hadn't noticed by now, I include a link to wherever it was that I found the material. This time, being caught up in the research I guess and my ensuing failure to find anything, caused me to forget to give y'all the link. Now I can't remember where it was that I got that information. :hb

It's most likely in my bookmarks folders, but there are probably thousands of those by now, so I'll have to sort through the history to see if I can find it again for you. ;)

_ken :w
Thanks, Guys for all the help! :)

Ken, that was really good reading. :_rock

My engine starts quickly and runs smoothly when cold. Warm, it seems to lean out a little and idle a little rougher. I think that the cold start injector is working right - it just leaks when it's off.

I get 26+ mpg on the freeway and 14 around town - can't keep my foot out of it.

I think I'm going to have to prove it to myself this weekend. I'll connect my fuel pressure gage to the rail, remove the cold start injector and reattach it to the rail facing out from the engine and turn on the fuel pump and see if it drips.

If it does, do you think a injector shop can clean it? If they can't, then I'll either have to live with it, or see how much TPIS wants to reflash my chip with a 89 map. The chip they custom did for me is really great.

I wonder if Corvette dropped the cold start injector because it is normally charged with fuel, heated by the engine and not flowing fuel.

I design Oil Refineries and have seen where ever there is hot gasoline and no flow it creates varnish where it hits the atmosphere, like at valve packing.

Gotta post this before AT&T Broadband looses their server like they did half way thru this post 1/2 hour ago. :hb

Fastvette86 said:
I get 26+ mpg on the freeway and 14 around town - can't keep my foot out of it.
You won't get very much more than that, if any at all. That is about the best mileage you can get out of a stock L98.

Gotta post this before AT&T Broadband looses their server like they did half way thru this post 1/2 hour ago. :hb

It wasn't just At&T! :eyerole :hb

_ken :w
Try The Last Detail , the last time I checked they had cold start injectors. I tried getting one from the dealer a few years ago and they wern't interested in finding one. Found that you can get them at AC-Delco authorized parts stores for 1/2 the price the dealer would have charged. As far as rebuild, I tried to get my cold start valve rebuilt but was told they are not rebuildable. Good luck
I have several cold start injectors that I have no use for pm me if interested
Craig sr

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