no computer...now what?

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
How do you diagnose the problem? Since obviously there are no computers on old trucks, and I'm looking at a early 1950-60s truck, How do you figure out what went wrong?

now I read this and I had to stop and wonder,
about the newer generations approach to vehicle maintenance,
and the mind set of the younger members, who never dealt ,
with a basic pre-computer controlled, non-efi engine.

yes its totally understandable if your less than 25 years old,
mostly because you were raised well after the majority of cars no longer were built using ,
the older basic automotive systems most of us older geezers were brought up working with.

you need too understand the basics of how an engine operates,
think logically and start with testing the basics
verify
hot ignition SPARK correctly timed at the spark plugs
consistent, FUEL,delivery and volume control
consistent ,and adequate cylinder to cylinder COMPRESSION
and yes theres the potential for mechanical based issues like a worn cam,
mis-adjusted valves , or sub systems like cooling or oil pressure
,the key, is, logically think things through, isolate and test, never assume anything, verify your results.

youll want to start verifying compression, verify you have fuel pressure,at the carb inlet port, verify the carb float levels are correct, verifying your ignition spark is arriving at the spark plugs and verifying the engines timing with a timing light.
the first step is to pull a plug wire off a spark plug and hold it by inserting a #2 Phillips screw driver blade with a plastic handle into the spark plug wire and holding the insulated handle while holding the exposed metal of the screw-driver shaft about 1/4" from the engines metal surface, and having someone try too start the car, the plug wire should arc to ground intermittently.
if you remove the fuel line from the carbs inlet port and add a 6 foot section of 3/8" rubber fuel line carefully and securely clamped to the existing fuel feed line , so you can allow the fuel pump to feed fuel into a empty 2 liter bottle it should fill that at least 1/2 and preferably totally in less than 45 seconds of cranking the engine on the starter.
you can pull each spark plug and use a compression tester to verify your getting compression, the results should not vary more than 5%-8% between cylinders.
a fuel pressure gauge,
feulpres.jpg

a multi meter,
image_12926.jpg

vacuum gauge,
vgauge.gif

a compression test kit,

62638.jpg

a leak-down test kit is optional but useful
62595.jpg

a timing light
timinglite4.jpg

and a dwell meter
dwellSL500_AA300_.jpg

https://itstillruns.com/use-tach-dwell-meter-5527498.html

https://www.howacarworks.com/ignition-system/checking-the-dwell-angle

http://garage.grumpysperformance.com/index.php?threads/sources-for-auto-tools.217/#post-70533

and you'll want too locate,
borrow or buy the tools required,
and do the research and read up on,
the instructions too correctly use those tools,
as that skill will prove very useful


step one would be to, verify exactly what your dealing with,
do a compression & LEAK DOWN test,
image_2899.jpg

http://garage.grumpysperformance.com/index.php?threads/leak-down-test.332/#post-14272
cylinder pressure can leak past the valve seats, past the rings, past a faulty head gasket and theres also potentially cracks in cylinder heads or bore walls,
but Id point out that failure to check all the cylinders renders any leak-down test basically less than useful.


and to
accurately measure the current cam lobe/valve lift,

http://www.igagingstore.com/MAGNETIC-BASE-FLEXIBLE-FLEX-ARM-001-DIAL-INDICAT-p/203957.htm
flexmagb.png

flexmagba.jpg

image_1450.jpg
18512.jpg

dial indicator with stand

verify the ignition timing advance curve
and post clear, detailed color pictures of your spark plugs, labled as to cylinder location.

what does a vacuum gauge show?

http://www.earlycuda.org/tech/vacuum2.htm
2713s.jpg

http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html
I got mine at harbor freight for about $19, and it works fine, sears sells the same gauge for a few dollars more and similar gauges are available at advance auto
READ THRU THE LINKS
http://www.sears.com/u-s-general-fuel-p ... 5887561009

http://www.secondchancegarage.com/public/186.cfm

http://www.sears.com/shc/s/p_10153_1260 ... 921x00003j

http://www.earlycuda.org/tech/vacuum2.htm

http://www.international-auto.com/fiat- ... gauges.cfm

vacuum.jpg

you can,t guess you need to deal in verified facts.
currently your don,t really know what your dealing with,
its physical operational condition or if you have worn cam lobes,leaking valves or worn rings etc
. it won,t do you much good too consider swapping cams,
until you've verified the basic engines operational condition tuning and compression, timing etc. is OK.

let us know What you find,
before we go further



http://garage.grumpysperformance.co...-running-up-to-expectations.14757/#post-81014

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/


http://garage.grumpysperformance.co...ng-carb-with-just-vac-gauge.14932/#post-84207

https://www.harborfreight.com/catalogsearch/result/index/?dir=asc&order=EAScore,f,EAFeatured+Weight,f,Sale+Rank,f&q=94190
related info


http://garage.grumpysperformance.co...se-valve-train-or-rod-knock.13846/#post-70866

http://garage.grumpysperformance.co...han-assume-you-know-answers.13217/#post-68926

http://garage.grumpysperformance.co...the-source-of-exhaust-smoke.13030/#post-67772

http://garage.grumpysperformance.com/index.php?threads/drop-back-to-basics.12943/#post-67323

http://garage.grumpysperformance.co...-t-get-it-running-correctly.12495/#post-62966

http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772

http://garage.grumpysperformance.co...n-jumping-in-with-both-feet.14918/#post-84129

http://garage.grumpysperformance.com/index.php?threads/blue-oil-smoke.12198/#post-59193

http://garage.grumpysperformance.com/index.php?threads/vacuum-gauge-help.9453/

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.co...and-a-bit-of-experience-make.6778/#post-21751

http://garage.grumpysperformance.co...em-will-eventually-cost-you.11810/#post-56635

http://garage.grumpysperformance.com/index.php?threads/the-trucks-just-not-running-well.13435/

http://garage.grumpysperformance.co...r-basic-performance-concepts.9731/#post-48391
 
Last edited:
Here is my 2¢
Remember that an internal combustion engine is essentially mechanical air pump. Each rotation of the crankshaft displaces a volume of air.
Basic:
Now to make any internal combustion engine work you need.
Air
Fuel
Compression
Ignition source
Timing of the above.

Clearly identify where and how your motor gets these items. This defines the starting point.

Being analytical (patient) always helps and if you need to guess at something ask yourself "what has changed that would cause this".
Asking this question and looking into it can help with a root cause.
Let's say you have fuel starvation so you diagnose the filter in the carb is dirty and you replace it. Fixed!
Did you ask "what change could have caused this"? If not your going to see the problem again. Is your fuel pump breaking down and plugging the filter, did you stop at a new gas station or use gas out of a can?

People seldom ever do this and I appreciate the difficulties of it. The fuel example above is not great for it but it applies all the time with electronics.
To prove you found the problem and not just a symptom of a bigger problem...
Once you "fix" it see if I you reinstate the symptom by backing out the fix. If you can then you know you can declare victory.

Cheers
 
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