Okay. I am about to light a pipe bomb in this old truck. I am getting so frustrated. I believe I am having a fuel delivery issue. The truck runs fine under 1/2 throttle or so when its warmed up. When its still cold it runs fine all the way through the rpm range. When it gets warm and I am trying to give it more than 1/2 throttle it stalls. I have checked all other systems to make sure they are accurate. Timing is set at 10 degrees. All cylinders have good pressure. (The rebuilt motor has maybe 500 miles on it now) All new ignition system other than the old distributor. Can the fuel pressure not be high enough? Also, my injectors are really noisy. You can here them ticking with the hood closed standing a few feet from the truck. Could my injectors be going bad?

Gary..I know you are reading this...do you have a fuel pressure tester? I need to make sure the fuel pressure is good at the rail.

I took off the smog and AIR system but retained the EGR valve. New headers and o2 sensor. I plan on converting to mass air once I get all the parts, but I just have a gut feeling I can make this thing run better on the speed density computer than it is currently running. Something just ain't right. I ported the E7TE heads and put long tubes on. I know speed density sucks, but I didn't change cams and compression or anything drastic, just smoothed out the intake and exhaust castings on the heads, bored .030 and installed the headers. I would think that it would run better. But it just seems underpowered. It also has a slight miss at idle and sometimes right when you start pressing the gas pedal it will hesitate and then come back to life.

Any help would be appreciated.

 

Ray,

You would really be doing yourself a favor if you included the basics -

- year & model of truck
- what engine

If I were to GUESS it'd be a 1986 F150 with some sort of V8, probably a 302 given that it apparently has EFI.

Have you asked the computer what *it* thinks is happening?

 

All that info is in my signature.That is a handy place to keep all that info I think. I will have to run the computer test on it.

 

A lot of us do the same, since it is quite handy for keeping the info handy. But, CT doesn't display sigs, along with a lot of other stuff. I think it has something to do with being on a crappy net connection.
Of course, being the truck is EFI, process of elimination should reveal that it would have to be either an 85 or 86, with a 302, since that was the only EFI engine used in these trucks, and the only 2 years it was used. Granted, there's always the possibility someone has converted a non EFI truck to EFI, but *most* of the time, they will actually mention that when asking for help......

As for the issue at hand, checking fuel pressure and computer codes is about the advice I can give, aside from the normal stuff like looking for a spark show at night, or a fuel line getting pinched and restricting the flow.

 

Yes, this is exactly correct! My net connection is sporadic, so I do what I can to reduce page load times.

Not having to download all the dancing images and extraneous text helps quite a bit.

Some guys here - Franklin2 & 81-F-150-Explorer for example - are still using DIALUP and have it sometimes worse than I do.

Yeah, and that's what I'm trying to encourage... When asking others for help, it helps THEM (those being asked) when all the needed and pertinent info is right there in their face and stated outright.

I used to display sigs, but some guys include multiple vehicles down there (and pictures of the kids, and whatever), and reading through all the text to try and determine which vehicle the OP is referring to can be a chore.

When asking for free help, it's best to reduce the work required of those who are being asked. State the pertinent facts outright, make it as easy as possible for somebody to help.

 

I would suggest a computer diagnostic, but it's really not going to do you much good, in my opinion, with the mods you have done.

One of the codes you should get will be a Code 44. Thermactor System malfunction. The Thermactor system is part of the Air Pump, and air injection system to the catalytic converters and/or exaust manifolds.

From all your mods, I would safely say that the computer is running in "limp home" mode. Everything is working at factory presets. That would mean no timing advance from the computer, and a preset fuel mixture ratio, ignoring the O2 sensor.

Just removing one smog component can really mess these older computer systems up.

Not saying you don't have other concerns, but the computer is going to be one of them. I would look into getting a performance or programable EFI computer system or something simular.

The stock computer will never run optimally without the stock exaust and backpressure, and the stock smog systems working.

 

Ray - Sorry I'm late to the party. Forgot to tell you why I'd be unavailable today, which was to visit Dad since I can't be with him on Father's Day. I'm back now and reading the mail.

Technically, no I don't have a fuel pressure gauge. But, I have gauges and lots of connectors so usually can figure something out. However, I've never checked fuel pressure on one of these trucks and don't know that we can for sure nor what the pressure should be.

But, 81-F-150-Explorer may have hit the nail on the head. You need to see what the computer is telling you, and I'm afraid he'll also be right on limp-home mode. The fact that things work well when the engine is cold says the computer is supplying ignition and fuel when it should at that point. But, when the computer determines the engine is warm enough and that it is time to go into closed-loop mode it finds out that things aren't kosher and goes into limp-home instead.

 

Im not so sure of this. I adjusted the timing the other day after driving home from work, so the engine was warmed up. I kept the timing light on the marks while revving the engine. The computer did advance the timing while revving. My CEL bulb is not installed, and I did read the thread on reading the engine codes. I haven't gotten around to doing it just yet. I need to get a bulb installed.

I switched to the rear tank today and the truck idles fine, but while on the rear tank I cannot accelerate or rev the engine. It does the exact same thing as the front tank only at 1/8th throttle. The front tank runs fine under normal driving conditions, just not under heavy acceleration. Are there two fuel pumps, one in each tank? The fuel lines going from the filter and reservoir up to the fuel rails look good.

i guess I need to figure out how to read the codes, the thread on code reading is not written very well in my opinion and is hard to follow. I will re-read it to see if I can figure it out. Wish I could just go to autozone and hook up a code reader.

 

Was it the computer, or was it the ignition module? Both are capable of doing a little timing advance.

Also did you adjust the timing with the Spout connector disconnected? This way the computer will not fight you when you do timing adjustments.

What CEL bulb?

If you are talking about the Check Engine Light, your truck doesn't have one. The first year of a check engine light on these trucks is 1988.

The best you have is a Emissions light, which is not hooked to your engine computer at all. All the emissions light does is to remind you to check the engine computer every 60,000 miles or so. The light is on a timer and it has to be reset. You reset the timer located under the dash with a pin.

To be able to read the codes, you will have to either buy a code reader, or use the multimeter method. There is no light hooked up to the computer to flash on your truck.

Yes there are two fuel pumps, one for each tank.

There are also sump filters, and a canister filter in the 6 port selector valve if I'm remembering rightly. Since it switches between tanks something tells me the filters on these could be begining to plug up, or engine heat affecting something.


They do have code readers at Autozone. For about $30 you can get one for your truck with an instruction book and everything, including what the codes mean.

Your truck will not run optimally without the smog components working 100%, with the stock engine computer and ignition system. Been dealing with these computer systems for years, and California smog laws.

The Computer runs in several different modes. Closed Loop optimal computer mode/ warm up mode which is a Open Loop mode / and Limp home mode which is also a Open loop mode. One uses the engine sensors to regulate the engine, the other two set everything at factory presets. If the computer isn't getting the right signals from the sensors, it will go into limp home mode if the truck is at operating temps. The truck is in warm up mode if the truck engine is below factory operating temps. Something as simple as a thermostat being too cold can keep your trucks computer from entering a closed loop operation.

Hope this helps...

 

I did adjust the timing with the spout connector unplugged. I was unaware that both the ignition module and computer advanced the timing. Is there a way to figure out if its just the module doing the advancing?

I thought I had a CEL, but I guess its just an emissions light. I wouldn't know because I have never seen it light up, I just remember seeing an empty light socket under the bezel when I had the dash apart.

I tried to hook all the smog stuff back up while rebuilding the engine, but it was either very expensive or almost impossible to find all the components. There was only one good piece of my old system, the cross over pipe that bolts to the back of the heads, it actually looked brand new, still had a readable sticker on it. The rest of the system was trash.

My next question is this: Will converting to Mass Air solve all my problems and make this thing run better? Can you run a later model MAF system without the AIR and EGR stuff?

 

Ray - I have an AIR pump in my bin of "removed and never to be used" stuff. In fact, I probably have all the bits you may need beyond the manifold, which you have.

Thinking about it more, I think you'll need the combo alternator/AIR pump bracket - which you saw sitting on my desk. I think you'll need that because I looked at your bracket and it didn't appear to have the bit for the pump.

 

I think I still have all the brackets for the whole system. If you don't mind, lets try throwing all that stuff back on my truck and see if it improves. the only problem we would have is the line coming up from the cat is no longer there. So we would have to drop the header and weld on a pipe nipple or nut for the tube that goes up to that diverter valve. Do you have the old exhaust system that would have that tube on it? We could just cut it off and weld it directly onto the header collector, then hook up the hose that goes to the diverter valve.

What kind of shape was your AIR pipe in? I am talking about the one that runs across the top of the passenger side exhaust back to the diverter valve. Mine was toasted. The only good items I have left are the check valve cross over pipe that connects the heads, and the large bracket that held the pump and alternator. I believe I still have the other brackets that go to the smog pump also.

You want to set up a time for me to come over this week and mess with it?

We still need to get those radius arm bushings installed. That kit I found on Craigslist was complete with just about every bushing. It had leaf spring bushings, radius arm bushings, cab mount bushings, tie rod end covers, and maybe more. Can't believe I paid only 40 bucks for it.

 

Not that I'm aware of no, as each are needed to be able to advance the timing. Full advancement goes through the computer during closed loop mode. In open loop, or limp home mode the computer predetermines the timing curve and fuel mixture by preset values and not actuall readings from the various sensors. This differes from the Ignition modules fail-safe mode where if no spout signal is recieved from the computer it uses the unconditioned PIP signal direct to the ignition module to control timing.

With a Duraspark-II for example, the module only does a small portion of advance. It controls most of the advance initial settings between Start or Run modes. Everything else goes through either the vacuum advance, or the centrifugal advance. The TFI-IV module functions very simularly to the DS-II, except the EEC-IV computer takes the place of the centrifugal and vacuum advance. The only way to check a DS-II module for advancement problems is to have it tested at the parts store. Some places can test the TFI-IV and some can't, but I doubt testing the TFI-IV will help you much.

Most likely the timer needs to be reset and they just pulled the bulb. It was a closely guarded secret in how those timers were reset so you had to go to the dealer to get it reset and the computer tested to make sure there were no smog problems.

It depends on the computer you use. There are EFI computers out there that do not need any smog devices at all to run properly. Most of these are aftermarket though, running aftermarket ignition systems. Ford Motorsport might have something. Most street legal factory equipped stuff is going to be smog dependant though.

 

The pipe I cut off with a tubing cutter, then flattened the stub and bent it over just above the exhaust pipe? I still have the majority of the piece, but it's been shortened w/said cutter on both ends. Don't think it's too useful - unless you run a shorter pipe and go onto that w/the hose.

Having said that, there's only one O2 sensor on this system - right? And, it is normally in the exhaust manifold, although you put yours in the headers. But, the point is that the computer has no way of knowing the oxygen is actually being injected into the cat - or am I missing something? If that's the case, can we trick it? Somewhere I have a book on the emissions system, so will take a look and see if it has clues.

Yes, we need to put the bushings in, and you did get a steal. But, hopefully you also got the axle bushings in that kit. Anyway, when do you want to work? Doing oil & filter change awa tire rotation on the wife's Subie today or tomorrow. Then will put brakes on it Wed or so, whenever they come in. Can't do Wed eve, but could most others this week.

 

Do you think we can take care of those bushings tomorrow evening? I would rather the truck not make all that noise first, then we can move to the smog system if we have time, or I can take all the parts and put them on whenever you are busy.

The axle bushings I do not believe were in the kit. I can get some though.

The system does have one o2 sensor. I cannot remember if the smog injects fresh air into the cat or pulls exhaust from it. If it injects fresh air I imagine we can just cap that port on the diverter valve and let the smog pump press fresh air into the heads only, there is nothing on the stock system that tells the computer that the fresh air is being injected into the cat. The only o2 sensor is in the manifold/header.