Holley Projection

[EasTXJEEPER]

My 83 Cherokee Laredo with a 360 had a non functional Holley Projection on it when I got it. It had been sitting since 98. Previous owner had almost 1 extra of everything except the TBI itself in a box on the back seat.
My gearhead son bugged it out and got it running, sort of. Replaced just about everything electrical (Fuel Pump, TPS, Temp Sensor) and it began to be dependable enough to satisfy my needs for performance and reliability.
Put $50 of premium in it for a short trip to a AMC Cruise-in two weeks ago and it ran well at highway speeds with the AC blowing cold air. I did note a falter or two on acceleration when merging on to freeway traffic.
Yesterday we gassed up for a fast interstate 20 run from Longview to Tyler State Park and noted again that if I stuck my foot in it it would falter.
On the way home we decided to take a scenic route being careful to ease into the throttle especially on acceleration from a dead stop. I was definitly not a stoplight racer at this point. I just wanted to get home before dark thirty. If you got on it even a little bit it would hesitate to the point of almost dieing dead in its tracks. The closer we got to home the worse it got. With just 3 more 4 way stops to go it died deader than a stone on acceleration. Managed to coast into somebodys driveway and get out of traffic. Tried to crank it and nothing. I could hear the fuel pump running and had over a half tank of gas.
Called my gearhead son to see if he could come trailer me home. He said try to crank it again with the throttle wide open. It finally fired up and we managed to get it home under its own power.
OK. What's the problem. Fuel Filter? I don't think so. It will run 75 all day no problem. It's more like too much fuel at low rpm under load and it simply floods itself out. Looking for answers.
Almost everyone says scrap the TBI and carburate it for everyday dependabiity. What say you?

[DarkMonohue]

Almost everyone says scrap the TBI and carburate it for everyday dependabiity. What say you?

Sounds like almost everyone is afraid to boldly step "forward" into 1980s technology. Keep that TBI!

NOTE: This is a long reply, but it is broken down into chunks so you can proceed step by step.

If I'm reading it right, the truck was running pretty well with the Projection unit, and then started getting more and more difficult to drive. Correct?

You mentioned that you floored the throttle to get the engine to start. Some EFI systems have a "flood clear" mode where they will not add fuel if the starter is engaged with the throttle wide open. This mimics the behavior of a carburetor and allows the driver to do what he'd normally do to start a flooded engine. I don't know if the Projection unit has this function or not, but it may.

I'm assuming for now that your Projection works this way. If so, you basically cleared a flood condition to get your engine to start, indicating there was too much fuel for the amount of air that the engine was getting.

If I understand correctly, your entire truck, including the Projection system, has been sitting since 1998. That's a long time for a fuel system to get crudded up. There is probably a lot of junk in the entire system. Fresh fuel could be loosening those deposits and flushing it forward to accumulate in the injectors or in the filter. If the filter has been on there since 1998, it's almost certainly full of junk, and is probably passing garbage from the downstream (clean) side of the filter element on to the injectors. It's worthwhile to replace the filter on principle alone.

I would also have a look at the injectors. Dirty injectors can actually run richer than clean ones because they don't close fully, and will continue to pass fuel even when they aren't supposed to (although they will flow less than they should when held open on 100% duty cycle). You might be able to bench test them to make sure they are flowing within spec and have the correct spray pattern. You can also send them out to WitchHunter for a very thorough cleaning and testing procedure, and the cost is very reasonable.

Some other questions to chew on:

Does your system require an oxygen sensor? If so, do you have one installed? Is it a known good unit? Is it wired correctly? Can you verify that the Projection controller (ECU) is getting a signal from it and responding appropriately?

Is the Projection controller properly grounded? How about your engine?

Does the Projection controller have solid and reliable sources of constant and switched power?

Are there any electrical faults such as loose or dirty connectors, possible shorts, frayed wires, etc that can be corrected?

Is your fuel pressure within specification? Does it remain correct even when your problem occurs?

Keep in mind that the initial tune your son put on the truck may have been effective with clogged injectors or other out-of-spec parts. If you correct those problems by replacing the bad parts, the truck will run poorly until it is re-tuned for the new ones. Don't get discouraged by that. It doesn't mean that the old parts were better - it's just that you'd compensated by tuning around them.

[jdaniel83]

I used to have a Pro-Jection system on my '89 and I had some similar issues to what you're having. Honestly, I never quite figured it out completely before I pulled it all off and went to a 4 bbl carb, but a few things that DarkMonohue mentioned did make things better. First, do you have the closed-loop system hooked up (oxygen sensor)? If so then try unplugging the oxygen sensor connector from the back of the ECU (which puts it back into open-loop mode) and see if that helps. If it does then it could be a bad O2 sensor.

If you don't have the oxygen sensor then I would start with checking all the ground wires/connections. Make sure all the grounds are clean and all the connections are good and tight. If that doesn't help then I would lean towards the injectors or maybe even the ECU itself. Mine was doing pretty much the exact same thing that yours is doing except that mine never died on me. It started hesisitating when accelerating and eventually it would occasionally not accelerate above 30-40 MPH. Unplugging the O2 sensor on mine helped at first but then it started doing it even in open-loop mode. I pretty much narrowed it down to the ECU after replacing everything else, but by then I had put so much money into it that I decided to pull it off and go with the carb instead.

[Tripwire]

What about a worn out throttle position sensor?

[PlasticBoob]

Yikes, quit applying carburetor logic here guys!

1) Is this the analog Pro-Jection? The best thing about EFI is that you are able to plug it into a computer and see what's wrong instantly - you shouldn't have to guess nearly as much as you do with a carburetor! That's the whole point! Ditch it and go with a standard GM TBI system, that way you even get a check engine light.

2) I doubt your particular engine takes Premium.

3) It was sitting since '98 but ran great up until you last got gas? Maybe you got a bad tank of gas?

I have no idea how to troubleshoot Holley Pro-Jection without an oscilloscope (and even then, good luck!), but it really shouldn't involve much guesswork. If you can't plug it into a laptop or connect it to a smartphone via Bluetooth, it's time to JUNK it! Totally not worth keeping it, in my opinion.

Say it's a 70* day and the engine is running sluggish and rich. You connect the laptop and see your air temperature sensor says it's -64* out. Well there you go, time for a new IAT sensor. No guessing. Leave that to our carb'd friends. I hear they're getting paid as much as lawyers these days!

[DarkMonohue]

Carburetor logic? Well, it's a fuel delivery system. Some of the same needs and principles apply. We may not be looking at a faulty electrical component.

I'm a Megasquirt guy, by the way.

[PlasticBoob]

I was half-joking. Just referring to all the guessing when we could have a pretty good picture of what's going on already if we could only get some sort of console or datalog.

[jdaniel83]

Chances are that it's the Holley Pro-Jection 2D system and yep it's an analog system so no laptop hookup. I agree with you that a GM TBI setup or the MegaSquirt should be more reliable and easier to tune (via laptop) if you know how to. That or he could go to a carburetor like I did. Just depends on what he feels more comfortable tuning or having someone tune for him. Personally, I found that replacing my Pro-Jection system with a 4 bbl carb gave me a lot better reliability and was/is easier for me to tune should I need to, but then again that's just me. Haven't tried to tune an EFI system via a laptop yet but I hear that it's not too difficult once you get the basics down. One of these days I hope to though.

[DarkMonohue]

I agree that access to data is definitely useful. Often it will give a pretty specific indication of a faulty component, as in PlasticBoob's example. What it doesn't always do is identify issues like incorrect fuel pressure, a clogged fuel filter, crap in the fuel injectors, weak connections, etc. Issues like that are not necessarily caused by a single "bad" part that can be replaced to make everything rosy again, and are not solved by more sophisticated management or easier tuning interface.

Sometimes caveman tech is warranted. OK, maybe not full caveman-grade, guess-and-replace methods, but dirty hands may be a necessary evil to get this thing working. It just seems hasty to throw out EFI (any EFI) or change management when the problem might be simple and cheap to correct via a little bit of old-school, hands-on diag.

[Tinkerjeep]

I do not run EFI...but...

A friend of mine who had been building Jeeps for years when I first got into mine decided to run a Holley Pro-Jection. This would have been around 1996-8. He hated it. Same issues.

There is a trend developing here: responses indicate the Holley Projection systems from that era when run on AMC v8s are not reliable.

If you can't find a solution for the Holley, the solution is to find a replacement for the Holley.

What's wrong with carbs again?

[PlasticBoob]

Yeah, to each their own, of course. Let me throw my little spiel for EFI, though.

I personally would just be very frustrated to have an EFI system that doesn't try to help me figure out what's wrong in any way. In fact, the Holley Pro-Jection tries to do the opposite - it hides the issue. Some guys are fine with that, some aren't. I don't think it's worth keeping for the reasons I've already mentioned, but also because it's old tech that was subpar even when it was new in the '90s.

Systems like the Holley Pro-Jection give EFI a bad name. It has the worst of all worlds, so going back to a carburetor might be a wiser decision. However, to put in a little elbow grease now and upgrade to a better, more modern management system will save a lot of troubleshooting time in the future. You'll be miles ahead of the carb guys at that point.

As I've said in other posts though: one can't just go into EFI without hitting the learning curve. You WILL have to know your way around a multimeter, know how to solder, and know how the system works. Otherwise when something very simple goes wrong, it will seem extraordinarily complex. The system will only be as reliable as your skills. Once it's set up correctly, however, you're on easy street. And to be honest, the same is true with a carb. You can't seriously say that tearing apart a carb and learning its intricacies (which vary from model to model) is any simpler than an EFI system. They're roughly equivalent, so you gotta pick your poison. May as well go modern.

Dark, you're right of course. Even the best EFI system is not going to keep you from doing some dirty work, but it will narrow things down a lot faster. So will designing the system properly: not being able to identify fuel pressure is a bad implementation of EFI on the owner's part - I have a cheapo Summit fuel pressure gauge attached at the TBI unit. It might be a bad idea to leave it installed, but it has been holding up to the heat and vibration for many, many years now. In any case, the gauge can also be removed and the fitting plugged until it needs to be installed for diagnosis.



We can quickly take a look at the underhood gauge to see we have the correct pressure. This should even help identify a clogged fuel filter some of the time. It isn't 100% but it eliminates a lot of things. If we do have the correct pressure, then we can look at the datalogs to make sure we have the correct sensor readings, pulsewidths, and duty cycle. If we do, then we know that the injectors are probably clogged. Of course their spray pattern can be checked with a glance under the hood as well.

OBD-II cars and some certain aftermarket EFI systems also have fuel pressure sensors that give you a readout on the laptop. Nice stuff, good stuff.

As Dark no doubt knows very well, the datalog will catch an amazing number of problems - even certain bad wiring and connections, if you know what you're looking for. For example, one day when I was still sorting out my EFI system, I was leaving school late at night. The truck was running great for a few minutes, but after I swung out onto the street, I instantly lost a lot of power, and the engine sounded like it had a bunch of dead cylinders. I hooked up the laptop, started a datalog, and saw that everything was good on the console. Sensors were fine, both injectors were being ordered to fire, and they were firing the right amount of fuel. I knew I had to have a mechanical issue with the injectors. Sure enough, it turns out that I had not made a good solder joint on one of the wires going to one of the injectors, and it had cracked and broken. Because only 1 injector was firing half the fuel, I was basically driving a 4 cylinder 401!!! My point is that I solved the problem in only a few minutes with the help of the ECU. I can't imagine how long it would have taken to find that cracked hidden wire under the loom if I didn't have help from the ECU. Yeah, I could have taken off the air cleaner and saw that only one injector was spraying. In fact, I did do that, just to verify what the ECU was telling me. But I probably wouldn't have done that until way later, because I "assumed" all my wiring was fine. The problem couldn't have been my work!


Some people are happier with trying to diagnose carb issues, though. In my opinion, TBI is the absolute best system there is for modest engines. It's a great hybrid between a carburetor and modern fuel injection. It's amazingly simple, has all of the good from the carb world and very little complexity from the EFI world.

Think about it - a small tank of pressurized fuel on the intake, constantly looping to and from the gas tank, with two "squirters" that fire in precisely the amount of atomized gasoline your engine needs, based on the temperature, load, etc. And we're not even talking timing yet! It doesn't get much simpler AND more reliable than that. I love my "digital carburetor"!

[Tinkerjeep]

I agree, EFi can be a real good improvement over a stock carb. And the way things are built these days, it takes some idiot-proofing out of the learning curve of EFI systems, but adds in other "gaps"...the digital age is scary to a lot of older guys, some others don't bat an eye about going full on EFI...and some others (here included) can tune a carb so you can't tell EFI from old-school carb on your engine performance. reliability wise.

Both option require familiarity with the general principal and problem areas of both types of fuel introduction.

I see it this way: If you don't want a $2000+ buy-in to drive your vehicle, learn how to tune a carb.
If you have a laptop and are computer savvy and like the idea of supertuning every little thing...and you want to spend the cash for it, go EFI.

The Projection system was developed long before every 12 year old had a smart phone and a laptop. My late Grandfather had (its now my Mom's) an Itasca motorhome...it has a 454 Chevy, no EGR, no smog stuff, HEI (IIRC) and a Holley Projection setup. WITH the in-cab control box. The box has a few rheostats on it to tune various aspects of the Holly system. The vehicle hasn't run since 1998. I'd like to think (if or when the vehicle is ever started and used) the Projection system is versatile enough to be useful, but if not...its carburetor time, baby.

[Carnuck]

I'd use a Megasquirt TBI box (@$300 when I checked a week ago) to run the Projection.

[jdaniel83]

I'd use a Megasquirt TBI box (@$300 when I checked a week ago) to run the Projection.

Wish I would have thought about that, but oh well. My Summit 600 has been very good to me so far. Just wish I could say the same about my ring and pinion, but that's a whole other story.

[HAARubicon]

I noticed my dad, the OP, has not responded, so I will chime in here.

First thing to note, he inherited the system from the original owner, so it was what was on the truck. It is the first gen analog projection system. He has replaced all components and have run many tests. What we have learned from another forum member is that the TPS is the weak link. It has been replaced, which seem to get it to run okay.

A couple of other things to note. Dad does not have 3 grand to throw at a new system. He also is 74, and does not have a laptop to go out and tune on this thing.

So I guess the question really is, for his occasional use, and limited budget, should he keep trying to get this outdated system to work, or put on a new carburetor (another outdated system) that he can probably better understand?

All he wants to do is be able to take a couple of 150 mile round trips a month and enjoy his Jeep. My poor mom has to say a prayer over it every time they go somewhere, and the source of the problem is the Fuel Delivery system. I feel as if a good quality carb will give him the reliability he needs.

But if someone has clear suggestion to make this system reliable, that would be ideal. I am not sure that answer exists.

So I guess a pole is in order. Which is better, an outdate projection, or a shiny new carb. A new EFI is not an option.