1988 Buick Century Not getting spark after replacing igniti

NOGARD666

MEMBER
1988 BUICK CENTURY
6 CYL
FWD
AUTOMATIC
160,000 MILES

I have a 1988 Buick Century Estate Wagon 3.8l V6 engine. I have replaced the Spark Plugs, Plug Wires, Ignition Control Module, all three Coil Packs, and the Crank Position Sensor and it is still not getting spark (was tested at the coils to rule out bad wires/plugs).

Just to be sure I had the new Ignition Control Module tested before installing and it tested as good. I am now at a loss as to what to check next.

4 Replies

JDL

MECHANIC
16,098 POSTS

Welcome to the forum, any trouble-codes? There are two voltage sources going to the ignition module, both pink wire with black tracer, terminal P and M. Should go hot when you turn on the key, are they hot? Also, without rpm signal, the ignition module doesn't know what to do, nor the pcm. That signal comes from the crank sensor, I'm not saying the new sensor is faulty, could be a wiring circuit problem.

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Saturday, December 19th, 2009 AT 10:45 AM

NOGARD666

MEMBER
3 POSTS

The diagnostic port on the car is not working. We have tried two different readers and get nothing from it.

As to the wiring on the new sensor, the O'Reilly site does suggest replacing the pigtail at the same time if the old one looks damaged. I inspected the old one as far back as I could and could not see any damage.

We tried to check the codes after I placed this post and since then I have spoken to the service department of the local Buick dealer. They suggested that if we can not see any obvious problems with the wiring to check the wiring to the ignition control module. They said two wires should be getting between 5 and 6 volts (5.5 is nominal) and if neither are getting power that it is most like the power control module (computer). They also said that for that year of Buick that around 150,000 miles the computers do tend to go out, though they could have simply been telling me that to get me to buy their new one for $151 before labor and taxes (the O'Reilly one is around $80).

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Saturday, December 19th, 2009 AT 3:58 PM

JDL

MECHANIC
16,098 POSTS

Hi, with bypass ignition, the ignition module controls spark during cranking, not the pcm. The two wires I suggested you check are fuse protected, battery voltage, use a testlite.

Above a certain rpm, the computer takes over the spark timing. Above a certain rpm, the computer sends 5 volt signal on the bypass circuit, tan wire with black tracer. That signal tells the ignition module to use the signal on the white wire for spark timing.

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Sunday, December 20th, 2009 AT 9:35 AM

NOGARD666

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3 POSTS

Thank you very much for your help.

We tried a third diagnostic reader and some how it worked (all 3 readers we tried were the proper OBD1) and the codes it gave us were 12 (normal always gives), 24, 41, and 44. The 24 code is the first O2 sensor, and either the 41 or 44 is the lower O2 sensor, leaving the last one which said the most common issue was the cam sensor, then gave like 5 other problems, so after destroying the old crank sensor to force it out and nearly breaking the new one to press it in the car fired right up first turn over.

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Sunday, December 20th, 2009 AT 10:05 AM