73.5 T Now starts but dies during warmup?

Hockey fan · 02-15-2003, 10:23 PM

Thanks to everyone for advice earlier in the week when my car was dead in the driveway.

I did get the car to start again today, but as with the last 2 times it started, it dies as soon as the temperature starts to climb a bit. (It reaches around 140 - 160 before it cuts out). The car will then not restart. I'm wondering if anyone thinks this is a fuel issue or an ignition problem.

Paperwork from previous owner shoes new WUR 6 months ago. Cap and rotor are new.

I'm not sure if I'm losing spark as car warms up (coil, Permatune, points) or if fuel delivery is somehow cutting out as car warms up. Tough to do much troubleshooting as once the car dies it won't restart.

Again, car is a 73.5 T with CIS.

Wild ideas welcomed. (Although offers of coming and taking the car as mentioned in the past will not be entertained

)

Thanks again,

Jeff

RSW · 02-16-2003, 12:25 AM

Hi Jeff,
I had a similar problem with my 1988 3.2.
It would start from cold and run ok, as temp began to rise the car would begin to run slightly rough and slow then stall. It would then not restart - untill it cooled down.

At first I thought it was the Cylinder head temp sensor (CHT) but it seed to behaving normally when I checked it with a ohm meter.
Does your car have the updated CHT? it will have 2 wires instead of just one if its the new sort.

I then checked to see if I was getting spark after the engine had stalled by pulling a plug lead and pluging a spare plug into it. I was getting spark but Iwas sure it was weak. I went on to check the fuel pump by bypassing it at the fues box.

Anyway, it turned out to be the rotor arm ad or Dist cap. I measured the resistace and it looked a bit high.
I guess that as the car warmed up the resistance increases and the car stalled.
I also changed the DME relay as part of the trouble shooting but this obviously didn't solve the problem.

I hope my description helps you solve your problem.

Richard

Jim Sims · 02-16-2003, 08:16 AM

This car (73.5 T) doesn't have a CHT sensor. How does the car run before it stalls? Is the idle rough? What is the engine speed during the idle? Do you have the start lever down by the hand brake pulled up when you start? Is it still pulled up when the engine stalls after warming up? How much fuel is in the tank? Do you know the time on the fuel pump? Is it original? Cheers, Jim

Hockey fan · 02-16-2003, 10:52 AM

Jim & Richard,

Thanks for the replies. The car starts with the hand throttle up. It runs a bit rough upon initial start but smooths out quite quickly. I adjust the throttle down as it starts to warm up keeping the idle around 2000 rpm. The throttle is still pulled up probably 1/4 when it dies. Fuel level is 3/4 tank. Not sure of the time on the fuel pump. I have records back to 1979 so I can look and see if it's ever been replaced.

Do you think it might be the WUR leaning out too much as it warms up? Or maybe the fuel pump weakening?

Thanks again for the tip. I hate to throw new parts at it before I'm sure where to start.

Jeff

Hockey fan · 02-16-2003, 01:50 PM

O.K., now we're back to officially "Dead in the driveway" status again.

This thing is starting to try my patience......

Jeff

Jim Sims · 02-16-2003, 02:18 PM

I also suspect the system is leaning out excessively as the engine warms causing it to stall. One cause of this too high of a WUR warm control pressure. This can be caused by a defective WUR or a blocked fuel return; either the line to the main fuel return line or the main fuel return line to the front gas tank. If the warm control pressure drops into the acceptable range (41 to 44 psi at idle) when the return line is opened then a blocked return line is likely to blame. Take caution opening the line under pressure; have somewhere for the fuel to go and watch out for fire. There is also a 2nd control pressure regulator for throttle valve compensation on the 73.5 and 74 CIS systems mounted on the throttle body shaft . Inside this device there is a cam operated by the shaft and the cam varies the spring pressure on a diaphram, lowering the control pressure (for enrichment) at idle and full throttle but raising the control pressure and leaning out the mixture at the throttle mid-range. If this is malfuntioning, it could also be causing the warm stall condition. One really needs a fuel pressure gage harness setup to efficiently trouble shoot these systems. Cheers, Jim

Hockey fan · 02-16-2003, 06:18 PM

Jim,

Thanks for the information. You've pointed out some things I was unaware of. More ammo for the troubleshooting.

Thanks again,

Jeff