can aftermarket alarms stop spark?

no spark, alarm cause this? I have heard.........

Run around the web and find the manufacturer for the alarm. They can tell you about the config of your system. New alarms can screw with about anything they are wired to.
Lojack and the new factory help systems can shut the car down remotely, and tell the cops where it is. ( wonder what else they can do without telling us?)

yes an alarm even old can do this..
if the alram has an outpu whether NO or NC it cand be switched and tapped into the ignition wire tot he coil or whatever you want it to go to eliminate startup. most alrm place dont got o that extent. the other ive heard is killing power to the fuel pump too.

my 10 year old code alarm has a starter interupt circuit, it usually allows the starter to engage, but not actually crank.

The alarm in my 88, dealer installed, had some kind of electronic switch (not a relay) hooked up as an interrupter to the the ignition module power in circuit. Larger yellow wire to the module, should have battery voltage with the key in the run position. Mine had the voltage, but little amperage. The in wire would actually intermittently pulse voltage when the motor was cranking.
I was getting a really weak spark, which turned out to be the alarm module.

Yes, I've seen this happen a number of times before. Usually happens when I'm working on a friend's car.....we pull the battery, do the work, install the battery, and no start. Then we find out that an alarm was installed at one time, resetting battery sets it off, and I get to crawl around under the dash listening to it scream in my ear while I try to trace and cut the correct wires. Usually does the trick!!

Some of them will also cut the power to the fuel pump. Ran into this problem when my old neighbor went to change the battery on his Passport. Unplugging the battery reset the system, and since he had bought the vehicle with the alarm already on it, we had no clue how to disable it, and the instruction booklet was n o help. We finally managed to disable the damn thing, but from unhooking the battery so many times and it messing with the fuel pump, the car ran like pure crap for about 5 minutes afterwards.

I hate just about every aftermarket alarm, simply because unless they were installed properly (which about 90% of them are NOT) they are a pain to work around when working on a car.

thank you all

uh i think (could be wrong)
but dont all after market alarms reset by turning the key 3 5 or 10 times to reset?
and factory ones you usually just have to lock and unlock the vehicle w key at drivers door
any one else?