Howell TBI

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highlander

highlander

Member
Apr 19, 2020
37
48
18
Madison, VA
Having trouble with, I think my fuel injection system. Symptom after 30 min - 90 min of running power drops off increasing in severity over a short time until engine backfires, and nearly stops running. Let everything cool to ambient temp and you get another run of normal operation till happens again. The hotter the day the less time before the troubles. Engine coolant temps are in the normal range and oil pressure normal. I thought had a bad ignition module or coil. So I changed the cap, HEI module, rotor and coil from NAPA parts...... zero change. Cleaned all the EFI plugs and connections and TBI itself....... zero change. Thinking it's the fuel pump, maybe it is weak gets hot and output goes haywire. I have had pump failures before but in the past it was instant off flame out. ( this is the 3rd pump in 20,000 miles )

Anybody with a Howell EFI have any experiences like this ?

Fred
 
What do your O2 sensor readings look like when it starts to run poor? I'd be streaming sensor data, and looking for something out of the ordinary. Is timing staying consistent? Does the MAP sensor still seem accurate at high temps?

A fuel pressure gauge would be helpful for eliminating pump issues.
 
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I have had issues with fuel when the day (and road) gets hot. I still haven't fully run it down, but I am confirming a similar issue. At first I thought it was going to be a venting or vapor lock issue (it's possible even with efi), but that doesn't seem to be it.
 
highlander said:
A fuel pressure test gauge is on the way from summit, and I just discovered the Howell system has an OBD connection and I have a reader. I'll look at that next.
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The Howell OBD connector is version 1 which came out in about 1988 and has limited information available.

OBD II came out in 1996 and has much more info available. Unless your reader can also do OBD ver 1, you won't be able to read it with an OBD 1 reader. There is windows software and cables available to read and log OBD 1 data.

Does your Howell ECM have a Dynamic EFI sticker on it? If so you have the EBL system and you will have a much easier time diagnosing this.
 
Do you have Eletronic spark control, 7 pin module or the non-electronic controls for the distributor 4 pin module? It could be the pickup coil shorting out or going open. In order to change you must disassemble the distributor.
 
I have stock HEI ignition and the Howell EFI I have is OBD 1, so my reader is not any help and there is no log accessible by me. I have an extra fuel pump, next week I should have time to replace it and do a test drive again. I will also check the vent lines for the fuel system maybe drive without the fuel cap see what happens.
 
highlander said:
I have stock HEI ignition and the Howell EFI I have is OBD 1, so my reader is not any help and there is no log accessible by me. I have an extra fuel pump, next week I should have time to replace it and do a test drive again. I will also check the vent lines for the fuel system maybe drive without the fuel cap see what happens.
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I _think_ there is an ALDL(?) reader that might be able to read data from the OBD1 port.

ALDLdroid - Android application for OBD-I GM ECUs (and more!)

ALDLdroid is an Android application for data logging and tuning your OBD-I vehicles.
www.aldldroid.com www.aldldroid.com
 
tmsnyder said:
I _think_ there is an ALDL(?) reader that might be able to read data from the OBD1 port.
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Here is a windoze program to read the OBD-1 port. I was using this back in 2009 when I first got my Howell system and before I changed to the EBL.

There is also a link to a page that shows you how to make a cable on that site. The cable uses RS232 serial port which a rarity on a laptop these days. I don't know if a serial to USB convertor cable will work with it.

 
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With a HEI distributor that has vacuum advance the lids to the pickup coil move every time vacuum changes and the vires have been known to fracture. You might want to replace the pickup coil.
 
HEI modules have been known to be faulty out of the box and thermal intermittents are common with them. Dick Paterson says, that when it looks like its a fuel problem, it's likely the ignition! But it seems like it could be a fuel pressure (pump) problem.

There is stuff called freeze spray that instantly cools electronic components used in diagnosing thermal intermittents. You could try cooling the HEI Module with the stuff and see if it starts up and runs again. Note that the distributor is hot and will reheat the module quickly.

Be careful when using gauges to measure fuel pressure. The fuel pressure pulses with the injectors opening and closing causing the tube in the gauge to fatigue and fail causing a fuel leak.
 
RF_Burns said:
Here is a windoze program to read the OBD-1 port. I was using this back in 2009 when I first got my Howell system and before I changed to the EBL.

There is also a link to a page that shows you how to make a cable on that site. The cable uses RS232 serial port which a rarity on a laptop these days. I don't know if a serial to USB convertor cable will work with it.

Click to expand...

A USB to RS232 adapter should work, I just used one the other day for a piece of lab equipment.
 
I think it is fuel related at this point. Even after having issues it will always start and Idle fine. Today I was busy moving my daughter home from college after her graduation. Should be able to change the fuel pump and filter in a day or two. Not trusting new ignition parts I bought from NAPA is a bummer. I did notice the coil that was originally in the system was heavier than the made in China NAPA replacement, very sad.

There is a little temptation to put a more modern fuel injection system in with a performance distributor as well. The Holley Sniper/ Hyper Spark looks simpler than what I'm running now.

When the Howell EFI was first installed years ago and right and up to last week I thought was a great must have upgrade. Instant starts with barely a full rotation of the engine, less gas smell, seemed like smoother power delivery. But with the trouble shooting at the moment I'm not so sure anymore. Also having some thoughts about returning to a carb with the appropriate anti vapor lock pumps. The goal really is just to have as reliable vehicle as possible not a hot rod.
 
highlander said:
There is a little temptation to put a more modern fuel injection system in with a performance distributor as well. The Holley Sniper/ Hyper Spark looks simpler than what I'm running now.
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A big issue with the aftermarket EFI kits is everything on them is proprietary. If you have an issue they want you to pull it and ship it back to the factory for repair. That's fine for hot-rodders and classic cars who's owners typically take them out for Sunday drives not too far from home. But we take these things a thousand miles from home.

The EBL was (and still is) a great upgrade with plenty of diagnostics. I've heard rumors about someone acquiring the technology. Otherwise I'd look at a MegaSquirt ECM which can use your existing sensors and throttle body, plus add spark control and has widespread support.
 
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Rember that the GM biased TBI systems are depended on volume. Put a fuel gauge on it and go drive it up a big hill. If the pressure drops, then you have a restriction. This system needs 12PSI. It needs 3/8 fuel feed line not the 5/16 line that Howels uses. I have changed countless fuel filters and pumps on these. Try and stay away from the Chinese parts.
 
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Biggamehunter said:
Rember that the GM biased TBI systems are depended on volume. Put a fuel gauge on it and go drive it up a big hill. If the pressure drops, then you have a restriction. This system needs 12PSI. It needs 3/8 fuel feed line not the 5/16 line that Howels uses. I have changed countless fuel filters and pumps on these. Try and stay away from the Chinese parts.
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Thanks, I'm sure this is the issue. I think my fuel filter has been on there for 20,000 miles. As it gets more restrictive might even cause vapor with heat as I drive. I also read on Howells page that the fuel tank selector valve can be faulty and cause a restriction. Ordering one of those too.
 
highlander said:
I also read on Howells page that the fuel tank selector valve can be faulty and cause a restriction. Ordering one of those too.
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If you eliminate the fuel selector valve and go with two pumps, you will have redundancy. If one pump is acting up, switch to the other pump and carry on.


I used AirTex pumps because they have built-in check valves, but I can't find their site in N. America now, only Europe. Maybe someone bought them and changed the name.
 
RF_Burns said:
If you eliminate the fuel selector valve and go with two pumps, you will have redundancy. If one pump is acting up, switch to the other pump and carry on.


I used AirTex pumps because they have built-in check valves, but I can't find their site in N. America now, only Europe. Maybe someone bought them and changed the name.
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Hi Bruce, it looks like Red is the signal wire from the selector switch. True?

What are you using for ground?

I love that pump setup, simple and clean.
 
IIRC the factory selector wire is black. I rerouted mine to my under-seat power distribution area so it could drive my dual-pump selector relay.
 
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