'75 Carrera hot start problem

[sceaf3]

Wayne,

I am at my wit's end with my hot start problem. When the car reaches normal operating temperarture, 210 degrees here in Fl, and then is allowed to heat sink for about 20 minutes, it doesn't want to start unless the throttle is held about 3/4 of the way down and it is cranked for a longer than normal time. Then it finally catches and pops and snaps for a while as if it is very flooded.

If the car is allowed to cool for about an hour it starts normally but still usally shows some very slight popping noises. It is possible that the sound that I identify as flooded is fuel returning to the system after pressure has been lost, but it sure pops and snaps just like a flooded car. If the car only sits for 5 minutes after getting to normal temp it will start right up.

It is loosing pressure on the control side and it seems as if the gas is being boiled out of the lines as it looses pressure and lowers the boiling point of the fuel. I have replaced the fuel pump check valve, fuel accumulator, fuel filter, thermo time switch, all fuel injectors, the warm up regulator and the cold start valve (which was leaking). The car runs perfect in every other respect, although cold starting in winter weather (50 degrees) is not perfectly smooth. It takes a few seconds of throttle jockying to keep it going immediately after start up, but then smoothes right out.

If the car is run to normal operating temperature, then shut down and one fuel injector is immediately removed and left out where it can cool, and after 20 minutes a heat sinked injector is pulled out and they are placed side by side, the cold injector sprays as soon as the fuel pump is switched on. The hot injector won't spray until the sensor plate is tickled up and down a few times.

I would appreciate any guidance you can give me as I have exhausted every other source. Jason at Pelican Parts suggested that I consult you.

Thanks

[sceaf3]

Wayne, my email is jmskelding@comcast.net. jmskelding@comcast.net

[pete3799]

State your problem as there are many here that can help you.
The more info the better.
Pictures are good too.

[sceaf3]

Wayne,

I am at my wit's end with my hot start problem. When the car reaches normal operating temperarture, 210 degrees here in Fl, and then is allowed to heat sink for about 20 minutes, it doesn't want to start unless the throttle is held about 3/4 of the way down and it is cranked for a longer than normal time. Then it finally catches and pops and snaps for a while as if it is very flooded.

If the car is allowed to cool for about an hour it starts normally but still usally shows some very slight popping noises. It is possible that the sound that I identify as flooded is fuel returning to the system after pressure has been lost, but it sure pops and snaps just like a flooded car. If the car only sits for 5 minutes after getting to normal temp it will start right up.

It is loosing pressure on the control side and it seems as if the gas is being boiled out of the lines as it looses pressure and lowers the boiling point of the fuel. I have replaced the fuel pump check valve, fuel accumulator, fuel filter, thermo time switch, all fuel injectors, the warm up regulator and the cold start valve (which was leaking). The car runs perfect in every other respect, although cold starting in winter weather (50 degrees) is not perfectly smooth. It takes a few seconds of throttle jockying to keep it going immediately after start up, but then smoothes right out.

If the car is run to normal operating temperature, then shut down and one fuel injector is immediately removed and left out where it can cool, and after 20 minutes a heat sinked injector is pulled out and they are placed side by side, the cold injector sprays as soon as the fuel pump is switched on. The hot injector won't spray until the sensor plate is tickled up and down a few times.

I would appreciate any guidance you can give me as I have exhausted every other source. Jason at Pelican Parts suggested that I consult you.

Thanks

[ossiblue]

Originally Posted by sceaf3

Wayne,

I am at my wit's end with my hot start problem. When the car reaches normal operating temperarture, 210 degrees here in Fl, and then is allowed to heat sink for about 20 minutes, it doesn't want to start unless the throttle is held about 3/4 of the way down and it is cranked for a longer than normal time. Then it finally catches and pops and snaps for a while as if it is very flooded.

If the car is allowed to cool for about an hour it starts normally but still usally shows some very slight popping noises. It is possible that the sound that I identify as flooded is fuel returning to the system after pressure has been lost, but it sure pops and snaps just like a flooded car. If the car only sits for 5 minutes after getting to normal temp it will start right up.

It is loosing pressure on the control side and it seems as if the gas is being boiled out of the lines as it looses pressure and lowers the boiling point of the fuel. I have replaced the fuel pump check valve, fuel accumulator, fuel filter, thermo time switch, all fuel injectors, the warm up regulator and the cold start valve (which was leaking). The car runs perfect in every other respect, although cold starting in winter weather (50 degrees) is not perfectly smooth. It takes a few seconds of throttle jockying to keep it going immediately after start up, but then smoothes right out.

If the car is run to normal operating temperature, then shut down and one fuel injector is immediately removed and left out where it can cool, and after 20 minutes a heat sinked injector is pulled out and they are placed side by side, the cold injector sprays as soon as the fuel pump is switched on. The hot injector won't spray until the sensor plate is tickled up and down a few times.

I would appreciate any guidance you can give me as I have exhausted every other source. Jason at Pelican Parts suggested that I consult you.

Thanks

You certainly have covered all the usual bases but the above paragraph stands out. Even though the 75 operates with the fuel pump running at the turn of the key, the injectors should not spray fuel unless the sensor plate is moved. From what you posted, unless I misunderstood, a cold injector will spray fuel as soon as the pump is turned on. If that's so, that is a fault. Further, you say the hot injectors will not spray until the sensor plate is "tickled up and down a few times." This, too is a fault as they should spray immediately upon movement of the sensor plate.

Your problem appears to be two-fold--injector(s) that spray without movement of the sensor plate, and injectors that will not spray unless the plate is moved several times. Did I understand correctly about the cold injector? If so, have you tried with another injector (as the one you used could be bad?) You still apparently do not have residual pressure as evidenced by the need to toy with the sensor plate to get fuel flow however, and you've covered all the usual suspects. My inclination would be to confirm the cold injector test again, using other injectors, and do a pressure check on the system to confirm the integrity of the parts you've replace. If all checks out, next stop may be the fuel distributor itself.

Your symptoms are consistent with (1) a leaking injector which leads to flooding, and (2) loss of residual pressure. If this were me, I'd tackle the injector first, making sure that all injectors do not leak or spray unless the sensor plate is moved. Following that, pressure checks on the system. Please post your results.

BTW, I just noticed you have another thread on this same subject. It would be better to delete it so anyone responding will have a complete history and all responses will be in one location.

[Wayne 962]

This is a super common problem with CIS systems. There is a fuel accumulator in the engine compartment which is supposed to hold pressure in the system when the ignition is shut off. This helps prevent the vapor lock that you are experiencing. Most people know this. What most people don't know is that there is a corresponding check valve located inside the fuel pump which holds the fuel pressure when the pump is off. If this valve is leaking then you will have this problem, even if you have a brand new accumulator. I suspect that your problem is either with the check valve in the fuel pump, or the accumulator itself.

-Wayne

[mspirito]

I had the same problem with a 74 and it was the check valve that is totally NLA for the 74 don't know about the 75.

[boyt911sc]

sceaf,

Check the residual fuel pressure. This the most prevalent culprit for hot start problem. You have replaced several key CIS components in your quest to fix the nagging problem but never mentioned about checking the fuel pressures (???). That's the first and foremost important information a fuel injection trouble shooter should know. Just my two cents.

Tony

[sceaf3]

Thanks Guys,
I forgot to mention in my post that the fuel accumulator and fuel pump check valve have also been replaced to no avail. The symptons act more like leaky fuel injectors than anything else, but I put in all new injectors as well as a cold start valve.
Any more thoughts?
Thanks,
Sceaf3

[CharlieB]

Don't forget the primary system pressure regulator located in the fuel distributor. It is basically a check valve for fuel return to the tank. If it is sticking or worn you'll lose fuel pressure almost instantly upon warm engine shutdown, thus no residual fuel pressure = no warm start!!

[prebordao]

I have a very similar problem on my 74'. After replacing the accumulator and the pump check valve (to no avail) I was thinking on putting some heat shielding around the fuel pump as it sits very close to the engine.
What about that check valve in the FD, does it exists also on a 74 ?

[ossiblue]

You haven't answered yet (post #5) and I still think you have two problems to deal with--a leaking injector and loss of residual pressure. Does the injector you used in the cold test spray fuel when the fuel pump is running, before lifting the sensor plate? That should not be happening. Since you appear to be losing residual pressure, you need to confirm that with a pressure gauge and since you replaced all the likely parts, your next stop is the fuel distributor. However, I would suggest you run diagnostic tests on the pump check valve and accumulator--using the test gauge--before moving on to the distributor.

[sceaf3]

Thanks to everyone who replied. I am going back to diagnostics to see if I can determine the point where I am loosing pressure. It seems like everything except the fuel distributor has been replaced! I will post again in a few days after the guages have been used.

Sceaf3

[Joe Bob]

Are you going to use a fuel gauge? It's pretty much the only way to diagnose it......

If not already mentioned, lifting the flap to turn on the fuel pump or using a shot of ether will typically get the engine started if you are stranded.

[sceaf3]

ossiblue,
I meant that the cold injector fires immediately upon moving the plate, the hot one is a no go until it is tickled several times. I am going back to the gauges to try and determine where the pressures loss is.
Thanks for your help.
sceaf3