'87 5KCSTQ reluctant to start cold

John Larson viejoloco at comcast.net
Thu Jan 8 16:29:21 PST 2015

On 1/8/2015 10:09 AM, cobram at juno.com wrote:
> I had a similar thing happen on the 200TQA many moons ago.  After much
> diagnosis and shotgunning, it turned out to be the fuel return valve at
> the fuel pump was a bit loose or defective and would lose pressure when
> the car sat.
> I found a copy of my old post about this:
> "When the return valve was loose, it took a whole lot more than 5 seconds
> to start, and wouldn't start at all depending on whether the engine was
> up to operating temperature or not.  That one was a btch to figure out,
> since the valve was failing intermittently, and would test fine.
> Check valve is something everyone should keep as a spare when you change
> fuel pumps (usually get a new one with fuel pump), I think it was around
> $35 as a separate item, and if you have one on hand, it's probably faster
> to just change for a known good one than to test it."
> Experience is the name everyone gives to their mistakes
> John Larson <viejoloco at comcast.net> writes:
>> Cold meaning "sitting until the engine is at ambient
>> temperature".  To answer another post, the fuel pump runs when the
>> car
>> is in a cranking situation.  Fuel pressures appear to be normal.
>> I'll
>> confirm that this morning.  Temps here are currently about 60
>> degrees.
> My helper/motivator and I were able to put a little time in on this today.  (I find having someone to keep me on track is almost a necessity, and this guy keeps me pretty focused besides being handy with a wrench and good at home upkeep and repairs.)  Opening the hood revealed the control pressure had NOT gone below 2 bar, nor had the system pressure.  Ideal for starting.  After digging around in what might be the world's most disjointed and thrown-together workshop manual, we found the CEL code tests in the ignition section and ran the output tests.  Everything works as it should, including the cold start valve, which cycled 10 times during the procedure.  The engine, of course, started right up.  I drove it for 5 minutes per the book, hitting full boost several times (LOVE those long curving on ramps!).  Came back, ran the input diagnostics.  No codes, appropriate stumble, clearing on restart.  The gauges are still in place, the car ready to try again in the morning.  It should be noted that the car started as is should once the CS valve had been cycled 10 times.  If this simply cleaned it, we win; if it's hard to start in the morning, I'll test the temp switch in the head, below and aft of the P/S pump bracket.  Looks pretty easy to get to if it's bad.  Might be harder to find the part number than to access the switch.

Thanks for the input to date.  I realize there aren't that many of us 
still working on T44s, as most of them seem to have gone away. This guy 
has a 5KQ, a 5KTQ, and a UR S4, as well as a 4KS and an 80.  Nice guy, 
nevertheless ...


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