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Fuel delivery issues (L-jet)
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MadMax78
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PostPosted: Wed Dec 27, 2017 7:15 am    Post subject: Fuel delivery issues (L-jet) Reply with quote

Hi all,

Recently ran into a little issue with the bus. At random moments the fuel delivery would go really lean (got AFR gauge under the dash). This happened on a few hour trip to the UK. During the trip the problem gradually got worse, to being almost undrivable when we arrived.

I pulled over on the highway earlier because the CHT was reading a very low temp on #3 (around 300F instead of the usual 370ish). I thought maybe the #3 injector or wiring was failing. Also the rear bumper was extremely hot and I was down on power. Anyway, fiddled with the FI injector connectors a bit and set off, problems solved. However, the problem soon returned.

We’ve had this very same issue earlier on one of our overland trips in Bolivia. Back then we bypassed the stock wiring and added a relay that would just switch the FI pump on whenever the ignition is on as a quick fix. This solved the issues back then. After that trip I reverted the wiring to stock and all was fine, so assumed it may have been a fuel or altitude issue back then.

However, now the same problem returned and the same fix (new bypass wiring to the pump) fixed it again.

I have now once again reverted to the stock wiring and checked all contacts. Made them all nice and shiny again and applied copper paste. Also opened up the double relay for inspection. The contacts on the FI relay seeemed to be slightly whiteish, so also sanded those a bit.

The bus runs fine again, but since the problem wasn’t constant, I’m not sure if I fixed it.

My question is, what could be there cause here? Because when the issue appeared the engine wouldn’t stall. However, manually killing the pump by moving the FI contact in the AFM, the engine immediately stops.

So that would mean the pump doesn’t stop entirely? At first I thought the engine may be able to run (poorly) on gravity pressure from a full fuel tank, but that doesn’t seem to be the case.

I’m a bit at loss here as to what the cause would be. I was hoping the above problem description may sound familiar to you guys. Any thoughts would be much appreciated!
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1978 T2b ASI Riviera Plan I // Camper Special with MegaSquirt Injection & Ignition // 091 with 5.14 R/P and Peloquins LSD
Powered by Just Kampers, German Supply , Busted Bus, Aircooled Technology & DIYAutoTune
2008: Amsterdam - Beijing - Olympics -- 17.500km
2010: Amsterdam - Cape Town - FIFA World Cup -- 26.000km
2014: New York - Rio de Janeiro - FIFA World Cup -- 27.000km
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SGKent Premium Member
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PostPosted: Wed Dec 27, 2017 7:54 am    Post subject: Re: Fuel delivery issues (L-jet) Reply with quote

just a wild ass guess but maybe bad wires or FI ground:

Quote:
Anyway, fiddled with the FI injector connectors a bit and set off, problems solved. However, the problem soon returned.


Or the fuel filter needs replacing - or the tank vents aren't venting.

Do check your points to be sure that they are properly gapped.
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Wildthings
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PostPosted: Wed Dec 27, 2017 8:47 am    Post subject: Re: Fuel delivery issues (L-jet) Reply with quote

Get a 0-60 psi gauge and 1.5+ meters of hose so someone can read the pressure while you are driving.
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airschooled Premium Member
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PostPosted: Wed Dec 27, 2017 9:11 am    Post subject: Re: Fuel delivery issues (L-jet) Reply with quote

Have you considered the fuel pump relay (double relay) trigger contacts inside the AFM? If they were corroded or not touching securely then the double relay could be shutting off intermittently. Also check to ensure the pins in the AFM plug to the pins (35 and 36 iirc) are fully seated and not backing out of their slots.

The injectors need pressure to fire, but their low cutoff point seems to vary from car to car, depending on condition of injectors, state of maintenance, and position of Mercury. Wink with an idling engine, cutting power to the fuel pump will give you a baseline time of how long your engine can run on residual fuel pressure. Some go about a second, and some last upwards of ten seconds. Perform the same test at 3,000 RPM to see how the engine behaves at speed with a fuel pump that loses power.

Robbie
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raygreenwood
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PostPosted: Wed Dec 27, 2017 8:38 pm    Post subject: Re: Fuel delivery issues (L-jet) Reply with quote

What copper pasts are you refering to?

The only type of product I have fkund anywhere that is actually certified for use on EFI contacts is an electrolyte product like Pro Gold (there are several out there).

An actual copper paste would be just about the worat thing you could put on efi connectors. Copper oxidizes with moisture.....and the oxidization/tarnish of copper is a non conductor. This is why all EFI connectors are plated. Ray
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MadMax78
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PostPosted: Thu Dec 28, 2017 4:09 am    Post subject: Re: Fuel delivery issues (L-jet) Reply with quote

asiab3 wrote:
Have you considered the fuel pump relay (double relay) trigger contacts inside the AFM? If they were corroded or not touching securely then the double relay could be shutting off intermittently. Also check to ensure the pins in the AFM plug to the pins (35 and 36 iirc) are fully seated and not backing out of their slots.

The injectors need pressure to fire, but their low cutoff point seems to vary from car to car, depending on condition of injectors, state of maintenance, and position of Mercury. Wink with an idling engine, cutting power to the fuel pump will give you a baseline time of how long your engine can run on residual fuel pressure. Some go about a second, and some last upwards of ten seconds. Perform the same test at 3,000 RPM to see how the engine behaves at speed with a fuel pump that loses power.

Robbie


Yep, I checked the AFM, it looks mint. Also the arm easily clears the contacts, so that seemed fine as well.

When I first had the problem reoccur, the engine would run and after a few seconds start running very lean. But the engine just kept idling forever. So it wasn't residual pressure, there was still some fuel, just not enough.

raygreenwood wrote:
What copper pasts are you refering to?

The only type of product I have fkund anywhere that is actually certified for use on EFI contacts is an electrolyte product like Pro Gold (there are several out there).

An actual copper paste would be just about the worat thing you could put on efi connectors. Copper oxidizes with moisture.....and the oxidization/tarnish of copper is a non conductor. This is why all EFI connectors are plated. Ray


I'm using copper grease. It's actually meant to prevent corrosion and keep out moisture. Not sure on it's conductive properties though...

Wildthings wrote:
Get a 0-60 psi gauge and 1.5+ meters of hose so someone can read the pressure while you are driving.


Recently ordered a fuel pressure regulator with fuel temp and pressure senders. I'm running Megasquirt, so hooking those up to the ECU so I'll be able see fuel pressure in the data logs. Should help with troubleshooting. Still waiting for it to ship though.

SGKent wrote:
just a wild ass guess but maybe bad wires or FI ground:

Quote:
Anyway, fiddled with the FI injector connectors a bit and set off, problems solved. However, the problem soon returned.


Or the fuel filter needs replacing - or the tank vents aren't venting.

Do check your points to be sure that they are properly gapped.


Could indeed be some grounding issue. I measured conductivity in all the related wiring whilst moving them about to check for cracks, but all looked fine.

Fuel filter and ignition didn't change with the bypass wiring to the pump, which fixed the issue. So I'd say stuff like ignition or filters are ruled out.
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1978 T2b ASI Riviera Plan I // Camper Special with MegaSquirt Injection & Ignition // 091 with 5.14 R/P and Peloquins LSD
Powered by Just Kampers, German Supply , Busted Bus, Aircooled Technology & DIYAutoTune
2008: Amsterdam - Beijing - Olympics -- 17.500km
2010: Amsterdam - Cape Town - FIFA World Cup -- 26.000km
2014: New York - Rio de Janeiro - FIFA World Cup -- 27.000km
http://www.oranjetrophy.nl
******************************************
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raygreenwood
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PostPosted: Thu Dec 28, 2017 7:47 am    Post subject: Re: Fuel delivery issues (L-jet) Reply with quote

MadMax78 wrote:
asiab3 wrote:
Have you considered the fuel pump relay (double relay) trigger contacts inside the AFM? If they were corroded or not touching securely then the double relay could be shutting off intermittently. Also check to ensure the pins in the AFM plug to the pins (35 and 36 iirc) are fully seated and not backing out of their slots.

The injectors need pressure to fire, but their low cutoff point seems to vary from car to car, depending on condition of injectors, state of maintenance, and position of Mercury. Wink with an idling engine, cutting power to the fuel pump will give you a baseline time of how long your engine can run on residual fuel pressure. Some go about a second, and some last upwards of ten seconds. Perform the same test at 3,000 RPM to see how the engine behaves at speed with a fuel pump that loses power.

Robbie


Yep, I checked the AFM, it looks mint. Also the arm easily clears the contacts, so that seemed fine as well.

When I first had the problem reoccur, the engine would run and after a few seconds start running very lean. But the engine just kept idling forever. So it wasn't residual pressure, there was still some fuel, just not enough.

raygreenwood wrote:
What copper pasts are you refering to?

The only type of product I have fkund anywhere that is actually certified for use on EFI contacts is an electrolyte product like Pro Gold (there are several out there).

An actual copper paste would be just about the worat thing you could put on efi connectors. Copper oxidizes with moisture.....and the oxidization/tarnish of copper is a non conductor. This is why all EFI connectors are plated. Ray


I'm using copper grease. It's actually meant to prevent corrosion and keep out moisture. Not sure on it's conductive properties though...

Wildthings wrote:
Get a 0-60 psi gauge and 1.5+ meters of hose so someone can read the pressure while you are driving.


Recently ordered a fuel pressure regulator with fuel temp and pressure senders. I'm running Megasquirt, so hooking those up to the ECU so I'll be able see fuel pressure in the data logs. Should help with troubleshooting. Still waiting for it to ship though.

SGKent wrote:
just a wild ass guess but maybe bad wires or FI ground:

Quote:
Anyway, fiddled with the FI injector connectors a bit and set off, problems solved. However, the problem soon returned.


Or the fuel filter needs replacing - or the tank vents aren't venting.

Do check your points to be sure that they are properly gapped.


Could indeed be some grounding issue. I measured conductivity in all the related wiring whilst moving them about to check for cracks, but all looked fine.

Fuel filter and ignition didn't change with the bypass wiring to the pump, which fixed the issue. So I'd say stuff like ignition or filters are ruled out.


You should not be using ANY GREASE on fuel injection terminals. Virtually all greases made....of any type....are DIELECTRIC to one degree or another.....most of them are highly dielectric.

Dielectric in a short definition means....DOES NOT CONDUCT ELECTRICITY.

Too many people get confused in this fact because they see spark plug BOOTS ....and marine and outdoor power terminals using dielectric grease.

With spark plugs it gets used ONLY on the boots. If you happen to get a,small wmoumt on the spark ppug connector itself.....the connector has enough surface area and connector pressure to scrape through enough of the grease to make a decent connection.
However On modern cars that use the spark plugs themselves for sensing cylinder condition....and are milivolt sensitive just like injection..... getting grease on the spark plug connector causes major running issues.

The same goes for larger connector systems that use wide blade connectors that usually list that dielectric grease is required.

The fuel injection connectors do not have enough tension in the female connector or enough surface area to use ANY type of grease on their terminals. I have seen no end to the connectivity problems caused by applying grease to EFI terminals.

There has never been any factory EFI system that used a grease on EFI terminals...even on the outside only for water proofing...because the risk of poor connectivity is huge. This is wby all L-jet connectors have an injection molded silicone gasket in the female plug.....so they are water resistant. Ray
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