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1997 F250HD 5.8 Running Poorly

The issue with old trucks is not knowing the condition of everything and everything can go wrong. I typically reach a point where you just stop and do a minor tear down. Pull the intake, new gaskets, clean all the passages for vacuum and egr.

Great time to put some new o-rings on the injectors, clean the screens, maybe flow test them/sonic clean/flush them.

Replace all the vacuum lines, full tune up, jam a new ignition module and pickup in the dizzy.

Sure this sounds like overkill but with these old trucks you either spend a weekend and some coin going through it or it just beats you to death one part at a time.

My S10 started to randomly shut off and sputter. Long story short rebuilt the dizzy and new sensors, all AC Delco. Yeah I can waste time trying to troubleshoot one part or I can replace it all since it's 30 years old and not super expensive.
 
Also make sure you have the correct tfi module in it.

That truck should have a black remote mount.

It SHOULD throw a code if the wrong one is in there, but never trust old stuff.
 
Would a 97 F250 have the black one thought? I thought the F250/350 never went OBD-II or Mass Air (except for Cali models).

Federal Emissions over 8500 GVWR should still be Speed Density and batch fire right up till the end of the body style in 97, so id think theyd still have the grey TFI module.
 
reptillikus said:
Would a 97 F250 have the black one thought? I thought the F250/350 never went OBD-II or Mass Air (except for Cali models).

Federal Emissions over 8500 GVWR should still be Speed Density and batch fire right up till the end of the body style in 97, so id think theyd still have the grey TFI module.
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Yes it would be black. 95 was the switch over point. It wasn't obd2 VS obd1. Pretty much everything switched in 1995 iirc.
My 95 f250 is black and it's fed/batch/SD/8800gvw
 
Interesting, didnt know. Ford changed the way the ignition module controls timing advance; i didnt realize they changed every platform, i thought it was only the OBD-II Mass Air trucks.
 
reptillikus said:
Interesting, didnt know. Ford changed the way the ignition module controls timing advance; i didnt realize they changed every platform, i thought it was only the OBD-II Mass Air trucks.
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Yea the big deal with the black is that they're ccd - computer controlled dwell. The eec controlled the coi dwell.

There was a small wiring change as well. I don't remember the exact details of it, but I believe the wire is either 12v on start (grey, pulls timing and add dwell for starting) or it's a ignition feedback circuit (black) ? Something like that.
 
I have the 88, 89, 90, 92, 96, & 97 EVTMs. Im sure its in there somewhere, i just never looked. My DD is a 96 bronco so obviously already mass air (w/ black module), and my 96 F250 is a Powerstroke so no distributor.

If anyone needs the diagrams then ill take pics of them and post em.
 
Ummduh said:
Yes it would be black. 95 was the switch over point. It wasn't obd2 VS obd1. Pretty much everything switched in 1995 iirc.
My 95 f250 is black and it's fed/batch/SD/8800gvw
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I believe the HD trucks never got OBD 2. My 96 250 is still TFI on the dizzy.
 
Need scan data, STFT, LTFT, fuel pressure, see what the O2’s are doing. Without that stuff you’re guessing, and like I tell all those guy’s… “guessing is expensive “, “how much can you afford “
I go through this every week with someone.

CF4656DC-FD3F-4770-A28D-B5DF7DA56A1A.jpeg
 
Gdogg said:
Need scan data, STFT, LTFT, fuel pressure, see what the O2’s are doing. Without that stuff you’re guessing, and like I tell all those guy’s… “guessing is expensive “, “how much can you afford “
I go through this every week with someone.
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There’s maybe $150 worth of sensors in the engine bay of this truck. Guessing is cheaper than a nice scan tool. :laughing:
 
arse_sidewards said:
There’s maybe $150 worth of sensors in the engine bay of this truck. Guessing is cheaper than a nice scan tool. :laughing:
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Not really, I like to nail every diagnosis. Without a scan tool and knowledge of how to use it you’ll never fix it right. I deal with guys like you every week, I wish I had all the money they waisted. All those chinesium parts are a bunch of garbage and usually create more problems.
I do this for a living, I have one on my scanners on a different vehicle every day and I’ve been doing since the 80’s.
I had 3 vehicles come in today, 2 of them have been to guys that shot the parts bazooka at them and finally gave up. I just laugh at the stupid shit I see.
 
Gdogg said:
Not really, I like to nail every diagnosis. Without a scan tool and knowledge of how to use it you’ll never fix it right. I deal with guys like you every week, I wish I had all the money they waisted. All those chinesium parts are a bunch of garbage and usually create more problems.
I do this for a living, I have one on my scanners on a different vehicle every day and I’ve been doing since the 80’s.
I had 3 vehicles come in today, 2 of them have been to guys that shot the parts bazooka at them and finally gave up. I just laugh at the stupid shit I see.
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What scanner can you use for the EECIV?
 
ORTitan said:
What scanner can you use for the EECIV?
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Some really old OEM shit you probably can't find anymore.

Or a multimeter and a lot of service literature.

Another reason the dumbass "hurr durr I'm jimmy numbers and I like to over-diagnose things because I can't see the forest for the trees" way of doing things is not appropriate here.

The best way to diagnose shit on an EEC-IV I've found is to unplug shit one at a time and note symptom changes. You'll narrow it to a sensor or two that way.
 
ORTitan said:
What scanner can you use for the EECIV?
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Snap On Modis, I even have an old Star Tester which is the OEM Ford scanner for the early 80’s through 95. You can buy these out of date Snap On scanners cheap on ebay.

Actually that 97 is OBDI, even though it has an OBDII connector.

Anybody who wants to learn scanners should go to YouTube and watch some videos, there are plenty of good vids there that explain it well. This is what I always recommend for guy’s wanting to get started.
 
Small update:

I put a fuel pressure gauge on it. At idle, I have 30 psi. WOT it goes to ~ 32. This is the case for both fuel pumps.

I think the next step is focusing on the vacuum lines or possibly verifying base timing as several have mentioned.

Here's a video, likely worthless to hear what's going on over the exhaust leak. :laughing:
 

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x2 on timing.

Have you stuck a vacuum gauge on it yet? Fuel pressure should change approximately the same amount as vacuum from idle to WOT and 2psi is a really small change. Either air is leaking into that vac line or you got really shitty vacuum.
 
arse_sidewards said:
x2 on timing.

Have you stuck a vacuum gauge on it yet? Fuel pressure should change approximately the same amount as vacuum from idle to WOT and 2psi is a really small change. Either air is leaking into that vac line or you got really shitty vacuum.
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I have a mighty vac with a gauge, I hope will work for that. I did replace the vac line from the fpr to manifold tree. So, that's confirmed good.

I'm hoping to dig into vac and timing after work if it's not dark.
 
30 psi fuel pressure is low. Should be 40 psi or a little more when running. Disconnect the vacuum from the fuel pressure regulator and plug the vacuum line and run it. You will see full pressure. If it’s still only 30-32 then you have a pump problem.

I’m assuming regular maintenance has been done and you are not fighting a clogged fuel filter.

You may still have a vacuum issue. And you should check base timing and regular tune up items.
 
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With 30 psi of fuel pressure I’m surprised it runs, make sure your gauge is accurate. If your gauge is good check the fuel filter then go to the pressure regulator. Usually when those regulators fail the pressure goes full blast… like 125psi.
 
I had a 97 F250 with the 460. It became a real dog (more so than ususal). It acted like a plugged cat but wasn't. It had low fuel pressure from a voltage drop to the fuel pumps. It was the tank selector switch had high resistance and finally went open, no voltage to the pumps.
 
ok i think ive got all this typed up correctly:


B0:
1. check for adequate fuel supply
2. key off
3. install fuel pressure gauge
4. install test lead to FP lead of VIP test connector (** personal note ** this is the same test connector you use to check the check engine codes.)
5. turn key to RUN position
6. ground test lead to run fuel pump (** personal note ** all this part does is to tell the fuel pump to run continuously for the test. this part is not necessary, as you could just turn the key on while watching the gauge.)
7. refer to fuel pressure specification table and check to determine if pressure is within acceptable limits. was pressure within acceptable limits? yes > GO to B4, no > GO to B1

B1:
1. pressure low but greater than 3 PSI? (indicates fuel pump is running but not enough pressure) yes > GO to B2, no > GO to B3

B2:
1. plugged fuel filter (replace filter and check again for proper pressure)
2. kinked/restricted fuel lines (visual inspection)
3. low voltage to fuel pump (should be within 0.5 volts of battery voltage at connector)
4. disconnect return fuel line and note if fuel is being returned during this low pressure condition. if fuel is being returned, replace pressure regulator. If service was required and made > RETURN to B0, if no service was required, > replace fuel pump and RETURN to B0.

B3 (electrical circuit check):
1. inertia switch open? (reset switch as required)
2. wiring at fuel pump/tank connector loose or open?
3. fuel pump ground connection at chassis loose or defective?
4. improper fuel pump relay operation? (should operate when FP (test) lead is grounded with ignition key in RUN position)
5. EEC relay not operating if fuel pump relay doesnt operate? service all electrical problems and > RETURN to B0, if no electrical defects have been found, and pump still wont run > REPLACE pump and RETEST per step B0.

B4 (check valve test):
1. remove ground from test lead and note pressure on gauge. pressure should remain within 2 PSI for 3 minutes after lead is ungrounded. is pressure within 2 psi? yes > GO to B6, no > GO to B5

B5:
1. fuel lines or connectors leaking?
2. disconnect fuel return line and plug engine side. momentarily activate fuel pump by grounding test lead. raise pressure to approximate operating pressure. repeat step B4. if pressure holds, replace regulator and repeat test B4. if service was made > GO to Step B0. if no problems were found, > Replace fuel pump and GO to step B0. if unit still fails step B4, there may be a leaking fuel injector or rail. CORRECT these problems and GO to step B4.

B6 (engine on test):
1.if engine is EFI, disconnect and plug the vacuum line connected to the pressure regulator.
2. start engine and run at idle. fuel pressure should be as indicated in chart for key on, engine off. Is the pressure in spec for key on, engine off? yes > GO to B8, no > GO to B7.

B7 (idle engine repair):
1. fuel filter restricted? (replace)
2. improper fuel regulator adjustment? (** personal note ** ignore this step, pressure regulator is not adjustable)
3. fuel line restricted?
4. improper voltage to fuel pump? (battery voltage at pump connections) if defect has been found and serviced > GO to B0, if no defect is found > replace fuel pump and GO to B0

B8 (high speed test):
1. with engine running at idle and vacuum line disconnected if necessary from step B6, note fuel rail pressure.
2. rapidly accelerate engine and watch fuel pressure. does pressure remain within 5 psi of starting pressure? yes > fuel pump is ok. if problem persists, CONSULT other parts of the manual. DISCONNECT test connections and RECONNECT vacuum lead if removed for test, no > GO to B7. (personal note if vacuum line is connected to regulator, pressure should increase when engine revs increase, if disconnected pressure should decrease when engine revs increase)
 
Update:

I suck at multi-quote more than OBS diag. Thanks to all that are trying to help, especially Rep with the pressure test details.

Base timing has been established.

All blind parts swapping have been R&R'ed to the originals with the exception of the EGR components that yielded no more cel.

On the onset, I tested and replaced the tps with a new parts store crap unit. I have zero confidence the new one is good.

I ordered a FoMoCo replacement from RA that'll be here early next week. I've elected to test the current one for failure and be able to slap the new one in place.

Between now and then, I'm going to identify any vacuum issues.

I believe the attached fuel pressures are in spec, albeit on the lower end.

Thanks for all the help.
 

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What does your pressure go to when you open the throttle?

When I got my truck, I had to change both the front and rear tanks in my 96 with the 5.8. It would idle fine, but anytime a load was on the engine it would struggle and seemed very choked up. Initial fuel pressure readings seemed alright and were identical tank-to-tank, but under throttle/load, it revealed both pumps were putting out all they possibly could. If you haven't already changed the fuel filter, do that. If you change a pump I recommend pulling the bed, it's easier.
 
I have a 1993 F150 5.0 4x4 with a completely rusted out cab. I ended up buying a 1995 f150 5.0 to do a cab swap. The engine/trans were removed prior to purchasing. It came with boxes of parts that I assumed were 5.0.

In my parts swapping prowess, I've verified same part numbers b/w 5.0 and 5.8 platforms via RA.

Hey, if it's disassembled in a box from the parts truck; why not.

Back to the '97 5.8 and the drivabilty issues. The throttle body in the parts box was loose and had better coolant nubs. I thought I'd swap that one in. Abandoned that when there weren't 2 driver side vacuum ports.

Fuck it, no big deal. I'll focus on cleaning the plates on the throttle body of the 5.8 prior to installing the FoMoCo tps. That's when I noticed 5.0 in the casting as pictured.

I'm beginning to think the previous owner put this TB in to make it get down the road. Maybe the IAC and TPS are correct for the 5.8 , maybe for the 5.0.

I don't have enough Ford experience to know what's right, outside of testing/replacing the existing.

Strangely enough, the TB from the parts truck is stamped 5.8.
 

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