time for a new ignition coil?

[novadmc]

lately my D has been a bit cantankerous to start whether cold or hot. lately its' taken one long crank if cold to fire up and 2 2-3sec cranks when hot. sometimes it would catch on 1st crank hot but not die within 2 secs. 2nd crank it would fire up slightly rough then calm down after a couple seconds. once running it would stay running.

not sure what to check first, i decided to clean as many contacts related to ignition/fuel as i could to see if that helps at all. ballast resistor, coil, all connectors around there, rpm relay & connector, etc (only thing i didnt get to was fuel pump itself).
after that the car did fire right up cold (1x 1-2sec crank) I let it run for a few mins then shut it off, waited 1-2 mins and tried again. again it fired right up with 1x 1-2sec crank.

all that said, i decided to also check resistance across the ballast and the coil just to make sure both were in spec.

ballast looked good at .5 - .6ohms.
coil readings were (everything disconnected from coil:
L.T.: .5 ohms
H.T.: 8900 ohms

the tech manual says it should read:
L.T.: 1 ohm
H.T.:7000 ohms

are those values indicative of a coil on its way out?

hopefully i took the readings correctly correctly for the coil
LT: multi-meter on + (15) and - (1) on coil
HT: multi-meter on + (15) and ignition coil socket

the coil does appear to be the original Bosch unit:
36116
(pic was taken before cleaning up the coils terminals. readings were taken after cleaning them up)

if those readings aren't good, what risk, if any other than crappy drivability) am i incurring by driving the car?
One of these days i still should pull the injectors and test spray pattern. i'm kicking myself for not doing that when i had the whole intake manifold ripped apart back in May.

thanks for any insight!

[David T]

lately my D has been a bit cantankerous to start whether cold or hot. lately its' taken one long crank if cold to fire up and 2 2-3sec cranks when hot. sometimes it would catch on 1st crank hot but not die within 2 secs. 2nd crank it would fire up slightly rough then calm down after a couple seconds. once running it would stay running.

not sure what to check first, i decided to clean as many contacts related to ignition/fuel as i could to see if that helps at all. ballast resistor, coil, all connectors around there, rpm relay & connector, etc (only thing i didnt get to was fuel pump itself).
after that the car did fire right up cold (1x 1-2sec crank) I let it run for a few mins then shut it off, waited 1-2 mins and tried again. again it fired right up with 1x 1-2sec crank.

all that said, i decided to also check resistance across the ballast and the coil just to make sure both were in spec.

ballast looked good at .5 - .6ohms.
coil readings were (everything disconnected from coil:
L.T.: .5 ohms
H.T.: 8900 ohms

the tech manual says it should read:
L.T.: 1 ohm
H.T.:7000 ohms

are those values indicative of a coil on its way out?

hopefully i took the readings correctly correctly for the coil
LT: multi-meter on + (15) and - (1) on coil
HT: multi-meter on + (15) and ignition coil socket

the coil does appear to be the original Bosch unit:
36116
(pic was taken before cleaning up the coils terminals. readings were taken after cleaning them up)

if those readings aren't good, what risk, if any other than crappy drivability) am i incurring by driving the car?
One of these days i still should pull the injectors and test spray pattern. i'm kicking myself for not doing that when i had the whole intake manifold ripped apart back in May.

thanks for any insight!

The typical symptoms of a failing coil is breakdown under high load and/or high RPM's. A 30 + year old coil can't be working like a new one but I don't think that is your immediate problem. I would be checking the fuel system starting with the CSV.