85 GT CFI stalls when it gets hot

On Wed, 22 Jun 2005 12:35:37 -0400, duvald rearranged some electrons to form:

Fuel filter?

"David M" wrote: > On Wed, 22 Jun 2005 12:35:37 -0400, duvald rearranged some > electrons to > form: > > > I just bought an 85 GT and when it has been running for > about 15 > > minutes it stalls at idle. As long as I keep the engine > revved up to > > about 1000 rpm it will keep running but rough. I?ve > replaced the > > plugs, plug wires, checked the distributor, replaced the > injectors and > > I wonder about the fuel pumps since it runs fine at idle at > first. > > When I try to restart after it stalls, it turns over very > slowly, like > > the battery is low. Once I let it sit for about 5 minutes, > it starts > > up and runs for about 15 minutes and then dies again. Any > suggestions > > would be greatly appreciated. > > Thanks, > > Jim > > Fuel filter? > -- > David M (dmacchiarolo) >

> T/S 53 > sled351 Linux 2.4.18-14 has been up 2 days 10:05

Thanks for responding Dave

I have a new fuel filter and intend to replace it but I figured if it was one of the fuel pumps I would avoid having to change the filter twice. I?ve also replaced the water pump and thermostat just to make sure it wasn?t creating a heat problem at the intake/injector body and I wasn?t sure if the fuel filter would cause the problem only when it got hot. Things are a bit pricey out here in Hawaii so I wanted to see if anyone else had experienced this problem before and would share the root cause of the problem before I get any more parts.

Thanks again, Jim

On Wed, 22 Jun 2005 19:36:01 -0400, duvald rearranged some electrons to form:

Maybe you should pull the codes before replacing any more parts.

I hate to tell you, but you started your problem diagnosis-by-replacing-parts at the wrond end. Do the fuel filter first.

Even better, get a fuel pressure guage and test fuel pressure at the CFI unit (assuming the fuel line has an accessible schraeder valve). Check a manual (Chiltons or Haynes) for proper fuel pressure if fuel pressure is low, replace the filter and recheck fuel pressure, if it is still low, you either have a bad fuel pump, or a blocked/pinched fuel line.

EVERY> "David M" wrote:

David M wrote in news:pan.2005.06.22.19.57.31.943420 @sled351:

How would a fuel filter cause the starter to spin slowly like the battery is running down?

My suggestion is the TFI module (Thick Film Ignition module.)

I'm not sure if that could cause the slow starter problem, but it could if the ignition is firing off time.

On Thu, 23 Jun 2005 05:24:00 +0000, elaich rearranged some electrons to form:

How would a TFI module cause the starter to spin slowly like the battery is running down?

David M wrote in news:pan.2005.06.23.10.08.03.390167 @sled351:

If the ignition is firing off time, it could cause preignition, and starter drag.

"cprice1" wrote: > I hate to tell you, but you started your problem > diagnosis-by-replacing-parts at the wrond end. Do the fuel > filter first. > > Even better, get a fuel pressure guage and test fuel pressure > at the > CFI unit (assuming the fuel line has an accessible schraeder > valve). > Check a manual (Chiltons or Haynes) for proper fuel pressure > if fuel > pressure is low, replace the filter and recheck fuel pressure, > if it is > still low, you either have a bad fuel pump, or a > blocked/pinched fuel line. > > EVERYONE: Did CFI cars have a low pressure return line in > addition to > the high pressure supply line? > > duvald wrote: > > > "David M" wrote: >  > > On Wed, 22 Jun 2005 12:35:37 -0400, duvald > rearranged some >  > > electrons to >  > > form: >  > > >   > > > I just bought an 85 GT and when it has been > running for >  > > about 15 >   > > > minutes it stalls at idle. As long as I > keep the engine >  > > revved up to >   > > > about 1000 rpm it will keep running but > rough. I?ve >  > > replaced the >   > > > plugs, plug wires, checked the distributor, > replaced the >  > > injectors and >   > > > I wonder about the fuel pumps since it runs > fine at idle at >  > > first. >   > > > When I try to restart after it stalls, it > turns over very >  > > slowly, like >   > > > the battery is low. Once I let it sit for > about 5 minutes, >  > > it starts >   > > > up and runs for about 15 minutes and then > dies again. Any >  > > suggestions >   > > > would be greatly appreciated. >   > > > Thanks, >   > > > Jim >  > > >  > > Fuel filter? >  > > -- >  > > David M (dmacchiarolo) >  > >

>  > > T/S 53 >  > > sled351 Linux 2.4.18-14 has been up 2 days 10:05 > > > > Thanks for responding Dave > > > > I have a new fuel filter and intend to replace it but I > figured if it > > was one of the fuel pumps I would avoid having to change the > filter > > twice. I?ve also replaced the water pump and thermostat > just to make > > sure it wasn?t creating a heat problem at the > intake/injector body and > > I wasn?t sure if the fuel filter would cause the problem > only when it > > got hot. Things are a bit pricey out here in Hawaii so I > wanted to > > see if anyone else had experienced this problem before and > would share > > the root cause of the problem before I get any more parts. > > > > Thanks again, > > Jim > >

I can get to the schrader valve with no problem, it?s right on top of the throttle body next to the injectors. I think checking the codes will probably tell me if anything like the TFI module is bad so I will try that as well.

I have read in other posts about keeping the fuel pump submerged in order to prevent premature failure and wonder if that might be a typical problem with older fuel injected cars?

Thanks for all the suggestions so far, I?ll keep you all informed on what comes of the troubleshooting effort. Jim

elaich wrote in news: snipped-for-privacy@individual.net:

1. The codes wont tell you if the TFI is bad, given your symptoms... Code readout hardly EVER shows up a bad tfi in EECIV
2. As pointed out, this sounds much like a older carbed car, save dying at fifteen minutes. - Havent I read somewhere that CFI's sometimes DO get vapor lock? Due to lower pressure? I wouldnt have one myself... The only advantage is the DONT have a power valve to blow out.

So I would Start by disabling the coil when it cranks hard.. if it then cranks normal, you know it's premature ignition. (A too-lean mixture, at firing time SOMETIMES might cause the same but that is a little unlikely.)

THEN disconnecting spout, and trying it, then borrowing a timing light. Make sure that it doesnt show more advance than 12 or so degrees while cranking. with spout disconnected

If it's NOT fuel related It might be the TFI, it might be the dist pickup, it might be timing... or a combination.

Backyard Mechanic wrote in news:Xns968176D02E00Dpettyfogyahoocom@207.115.63.158:

I only mentioned the TFI because it's notorious for causing intermittent stalling. I had an '83 that had a bad one, but the engine never dragged when trying to restart. It just wouldn't fire.

The starter dragging symptom is hard to get a read on. It occured to me that the TFI 'might' cause the timing to be off and was causing preignition, which could cause starter drag. I don't even know it that's possible.

"Backyard Mechanic" wrote: > elaich wrote in news: snipped-for-privacy@individual.net: > > > David M < snipped-for-privacy@nospam.com> wrote in > > news:pan.2005.06.23.10.08.03.390167 @sled351: > > >  >> How would a TFI module cause the starter to spin > slowly like >  >> the battery is running down? > > > > If the ignition is firing off time, it could cause > preignition, and > > starter drag. > > > > 1. The codes wont tell you if the TFI is bad, given your > symptoms... Code > readout hardly EVER shows up a bad tfi in EECIV > > 2. As pointed out, this sounds much like a older carbed car, > save dying > at fifteen minutes. > - Havent I read somewhere that CFI's sometimes DO get vapor > lock? Due to > lower pressure? > I wouldnt have one myself... The only advantage is the DONT > have a power > valve to blow out. > > So I would Start by disabling the coil when it cranks hard.. > if it then > cranks normal, you know it's premature ignition. (A too-lean > mixture, at > firing time SOMETIMES might cause the same but that is a > little > unlikely.) > > THEN disconnecting spout, and trying it, then borrowing a > timing light. > Make sure that it doesnt show more advance than 12 or so > degrees while > cranking. with spout disconnected > > If it's NOT fuel related It might be the TFI, it might be the > dist > pickup, it might be timing... or a combination.

I am inclined to believe the slow starter problem is heat related and is seperate from the stalling/fuel problem but I?m willing to consider anything and everything at this point. The starter works fine when it cools down and if the replacement starter spins fast enought when hot, it might restart the car. I?m gathering all my equipment and I will try the fuel filter first, then check the fuel pressure after it heats up. If the timing is set properly and disconnecting the coil causes the starter to spin at the correct speed, should I replace the TFI next or look elsewhere.

I really appreciate all the assistance from everyone, thanks for taking the time to help me out. Jim