[Neophyte]

I have a 91 TBI motor which I'm trying to start. It has an aftermarket computer. The injectors do give a pulse of fuel when switching on but it sounds like I'm getting no spark as there's no indication whatsoever that it wants to start.

How do I check if the coil is getting a signal from the dizzy and also if the coil is actually "firing"???

[docvette]

Doc here,

Easiest way is too put a timing light on any plug wire and crank it, If it strobes during crank, you have fire...(this way you don't get knocked on your butt holding a plug and wire off ground)

Have you tried Start fluid down the TBI Throat? If it fires for a brief period, then your Spark delivery system is good...Look at the fuel system.

Is this engine a "Transplant" into something else...Or did you just have to replace the computer?

Doc

[Neophyte]

Thanks Doc,

Was hoping you would reply.

Yes, this engine is a transplant into a 53 Chevy 210 4dr. Some V8 shops over here import "complete" motors with trannys from the U.S. which are unfortunately just "cut" from the donor vehicles. Mine was complete except for standard air-filter housing and ECU. Also the wiring harnesses aren't unplugged neatly from the vehicles but just cut.

Unfortunately I didn't have any starting fluid on hand but poured a few drops of fuel down it's throat. Just the same cranking tone. I did put a screw driver into the dizzy side of the coil lead and held it close to ground and didn't seem to get a spark. I will however try a strobe too which I think is a good idea. Never actually thought of checking for spark that way before.

[Neophyte]

Well, still have no spark. Doc, do you know by any chance how I can trigger the coil manualy or know of a good TBI resource to refer me to?

[docvette]

Doc here,

If your still not getting spark, Then First thing to do is pull the ECM from the distributer replace or have it tested at your local auto parts shop, and if you get a new one, have them TEST the new one as well, about 1 in 3 are bad out of the box!...Have them test it several times to be sure it won't fail under heat. This will kill spark.

Next If that won't Cure the problem, Does this Have A Crank position Sensor? If so, Check to be sure it is operating, and adjusted properly. This will kill spark also.

If all thats good, Test the Megnetic pickup and reluctor inside the distributor (electronic points) If it has failed, ( and I know you don't want to hear this..) you have to pull the distributor, disassemble it to get the "Ring" or pickup out...and the new one in...reassemble the distributor and re install it.

If all is good, and STILL no spark, Check the coil, I'm assuming were talking about a 350 SBC with HEI (since you never said what engine it was...) With an Ohm meter, set for auto range or Rx10k measure between the BATT terminal and the Rotor pickup inside the Cap, It should read between 6,000 ohms to 30,000 ohms, Next measure between the TACH terminal and the Rotor pickup, and it should read the same. Anything above or below those readings , replace the coil.

Check all your fuses, especially those marked ECM, Computer, CCR, INJ1, INJ2,(I assume you transplanted the fuse panel and harness as well)

Try those in the order easiest for you to test in, and tell us what you find.

Doc

Photos:Fuses good/ blown
HEI Exploded View
Fuse Panel

[Neophyte]

Doc, the engine is a 91 SBC 350 TBI engine. Sorry, I didn't specify properly what engine I have. I only said it was a 91 TBI motor.

The coil is a smallish square coil sitting outside the distributor, just in front of it. There's also no crank sensor.

Unfortunately I wasn't lucky enough to get the harness and computer too. The importer reckons those don't come with when they import the motors from the states. I had to put an aftermarket programmable computer on. We did have some hassle with to start with as the signal from the distributor to the computer wasn't strong enough to trigger it so I didn't get any fuel as well. The guys then amplified that signal so now I've got fuel but still no spark. Can it therefore be assumed that the distributor module is bad causing it not to trigger the coil?

Fortunately there's an auto electrical shop close by that specialises in U.S. cars. I'll take the distributor there to have it tested.

Do you perhaps know how I can trigger this coil manually?

[docvette]

Doc here,

The module is ONE of the items that will kill spark. If you have a place that will test it do so...It will eliminate one link in the chain.

Find the wire that goes from the coil secondary to the mag pickup in the distributor, disconnect it and quickly ground it a few times , you should get high tension spark from the coil..If not, Check the mag pick~up & pole piece and/or replace the coil.

The lack of or weak Injector Reference pulse before is a clue, as it's signal is generated from the ECM to sync injectors to ignition..at the computer. you might want to look into why the signal there was attenuated.

Check the module first...It should be free, and easy to do. Don't forget lots of heat sink compound when re~installing it!

After that look at the Mag pick~up and pole piece..for operation, and "Air Gap" adjustment.

One of those should get you running.

Doc

[Neophyte]

Thanks Doc, I'll try to have the stuff tested tomorrow or Friday and let you know.