louderr57

Hi we had a starting problem with our 85 5.0 EFI it used to fire right off and run perfect. with no warning in this winter weather it decided to start taking a lot longer to fire off. we replaced the wires, plugs, dist. cap and rotor. still took almost killing the battery to finally start. so we replaced the coil. still didn't fire right off. so we went and replaced the Control module yesterday and it fired right up. So my son drove it around and it was great as usual until this morning on the way to school when he got up to 45mph or higher it would cut out or hiccup with a feeling like the engine stopped then started again. as long as we keep it under 45 it is fine. Filters are all clear and high pressure pump is working fine. was wondering if it could be the Fuel pressure modulator valve mounted upside down on the fuel rail?? I do not have access to a pressure gauge for this. I am stumped for the moment.

louderr57

forgot to mention we replaced the front tank last year and the internal pump set. the rear tank is disconnected after passing smog last year. runs very smooth and idles perfectly forever. just when you keep it at 45 it cuts out then goes again. Not filters or pumps. Until this it had been running perfect for the last year. It feels more like a cut out or a hiccup for a second.
Thanks.

louderr57

Update. This morning I took it to a tranny shop in town where an older guy who loves Fords took it for a test drive. He told me that the tranny was fine and that at about 45-55mph he would give it just a little more gas, just a little pressure on the pedal and it would hiccup, he said it was like it was leaning out for just a moment then fattening right back up again. all of this when it does happen takes approx. less than a second. The only thing I haven't changed was the Fuel pressure regulator. and the high pressure pump. Is there anything else it could be??? I just bought a Fuel pressure regulator and I am going to change it out and see if that makes a difference if nothing else I will have a bunch of new parts on the truck. I need to find out the problem. I am going to buy a fuel pressure gauge as soon as I get paid.

klricks

Are you sure the dash tank select switch is in the correct position?
Even though you say the rear tank has been disconnected, the tank select switch on the dash must always be set correctly or properly bypassed.
If not then the in-tank pump will not be running which will cause the fuel starving problems at higher speeds.

88xlt

I would put a container of name brand fuel injector cleaner in the gas tank. Just follow the directions on the container.

louderr57

The fuel tank switch is in the front tank position, Thank you. I ran some Lucas injector cleaner through it. I took it in this morning to our local shop and the smog guy looked at it. I asked him to see if he could pull some codes for me. The codes were the EGR sensor out of range, also he said I should check the crank shaft sensor. How can I test the crank shaft sensor?? he said that would be the only thing left that would cut the spark completely then let it start again running correctly. I also am having trouble getting the temp. control sensor out. It seems the brass nut is BETWEEN 15/16 AND 1" BUT I CAN'T GET IT LOOSE. ANY IDEAS. I soaked it for an hour in penetrating oil cant budge it. I bought a new one as he said that may be why I have to crank it so much in the mornings only. Thanks for replying. anyone else?? I did find the green little air tube going to the EGR sensor was split. I replaced that and hopefully that should fix the EGR code. it had no vacuum there with it cut in half. lol

88xlt

As far as the crank sensor, if it's acting up intermittently there would probably be no effective way to test it. If it wasn't acting up when being tested it would likely test good regardless. If you trust the mechanic the best thing to do would be replace it.

I thought your mechanic was all wet, telling you about the crank sensor. I didn't think they existed until the last half of the 1990s. Rockauto does show such an animal for your 1985.

As far as your temperature sensor, are you using a 6 point socket rather than a 12 point socket? If it is between sizes maybe it's a metric size. At any rate I would use a 6 point socket.

louderr57

I took the new one to the hardware store and it seems to be a 25mm. which I do not have. I have boogered it up so bad that I am at the point of vice grips, but it is in there and probably the stock one that came with the truck. I can't get it out. I know this is why it is hard starting in the cold mornings. Thanks for all your help. as far as the crank sensor I am going to just replace it because I am sure it is the original one and it really is the only thing left that could make the truck completely cut out for a micro second and then back on. I have just about replaced everything that can be replaced with the exception of the part I cant get off and the crank sensor. Otherwise when the truck is started it runs so good. the codes that were pulled were 21,30 and 33.
Thanks for the code link.

Lou

vjsimone

“replaced the front tank
“replaced internal pump set.

“taking a lot longer to fire off.

“replaced the wires, plugs, dist. cap and rotor “no change
“replaced the coil “no change
“replaced the Control module ? “it fired right up (Where was this??)

“45mph or higher it would cut out or hiccup with a feeling like the engine stopped then started again. (What are your RPMs at 45 mph?)

“under 45 it is fine

“Fuel pressure modulator valve (well it’s 32 years old, why not change it)
(When you pull the vacuum line off of it, does it show or smell of gas?)

“I do not have access to a pressure gauge for this. (No place to connect it anyway) high pressure pump? (You need 39psi do you think you have that?)

crank shaft sensor?
How can I test the crank shaft sensor?? http://easyautodiagnostics.com/ford/...module-tests-1
("The TFI-IV ICM is mounted on the distributor and has three pins, which plug into the Hall Effect camshaft position sensor (commonly known as the PIP or Profile Ignition Pickup sensor) inside the distributor.")

“temp. control sensor?
You have 2 Temp Sensors; Engine Coolant Temp and Air Charge Temp, both effect Fuel/Air mixture, and should be replaced.

“Otherwise when the truck is started it runs so good
(But you said you have a problem at 45mph accelerating, do you still?)

“The codes were the EGR sensor out of range
21 – Engine Coolant Temp Sensor (fix this code first, lowest number)
30 - ?? No such code
33 – EGR could be stuck a bit open, these old EGRs are always a problem and should be replaced. Causes hard starting and initial acceleration stumbling.

Recommend using some Starting Fluid spray and check all of your vacuum lines, emission devices and around your intake manifold.

The MAF sensor is another device that effects Initial Cold Start-up.

The Air Controller (Throttle Air Bypass Valve Solenoid (TABVS)(ISC-BPA)) should be checked and cleaned, make sure the valve is free.

TPS – When Throttle is closed, so the output should be 1.0 vdc on the TPS sensor.