Starting a fresh rebuild

rx4ur7 · 05-12-2009, 01:15 PM

A way to test injectors, remove rail to check operation, spray pattern and rate of flow.
4B-74/75 FSM 1988 F1-56 FSM 1990

Connector not on properly, think I mentioned that in a previous post. Common.

Same issue I had with my GSL-SE. Except the plug was on fine but the wire was broken under the insulation. As I probed for signal an inch away from the connector it showed correct readings. When I took the connector off and tested it the signals were intermittent. When I pulled on the wiring the insulation stretched, found the problem.

Two weeks ago had an FC that had intermittent running problems. On that one found a primary injector plug that wasn’t clicked on. He would hit a bump and it would start running bad, hit another and it would run fine. Had some other issues like fuel around injectors so had to replace all of the injector seals and orings. After replacing them and making sure all injector connectors were on it starts and runs great. We were also getting air past the injectors before replacing rubber. This was on a factory car that had never had to have any work done under the manifold. So it came from the factory this way. Amazed that it ran fine all these years. I was going to condemn the water temp connector (have seen plenty of them) because I could get it to run good or bad by playing with the wire, what I was doing was moving the injector wire at the same time. But couldn't tell it was injector until I pulled the manifold. Did not expect to find it not on completely.

This is one thing I have found on working on cars all this time, most running or starting issues are related to a missing or bad ground somewhere or one wire mucked up somewhere. Especially after an install where the vehicle was running before any work was done. This is based on working on factory platforms. When wholesale changes have been made all bets are off. But still comes down to comp, fuel and fire.

The FC3S is especially finicky with proper voltage and ground issues they are electronically overloaded as far as I am concerned. If they drop below 10V during cranking you will have starting problems flooding in particular. The ignition system really needs over 10v during cranking to give good spark. The motor also needs to be spinning fast enough. If it is 200rpm or less you can have starting problems, especially if compression is marginal.

Having a multitude of little problems ranks up there with something that has not been taken care of for a long time or someone else that is not familiar with it has done the work. I have seen my share of those. Have a turbo buggy in here now that was one of those. Mostly age and vibration related failures. Previous owners just drove it hard and put it away hot. (Not the 2 seater that is shown on the website)

Check and double check everything when you put the thing back together. Slow down to go fast. Also recommend sober and fresh.

Congrates on finding it.

vex · 05-12-2009, 01:29 PM

For more clarification, this wasn't the injector plug which you were referencing. This was a body harness plug close to the ecu which was only partially together.

Good read though none the less.

rx4ur7 · 05-12-2009, 02:00 PM

Ah ha, Sorry about that then. Pretty much same thing though. There was one that I had that one of the wires had pulled out a little from the harness connector. Connector was clicked on and tight. That one had me going for a while.

Enjoy your ride now.

05-12-2009, 01:15 PM	#31
rx4ur7 Rotary since 1972 Join Date: Nov 2008 Location: Tucson iTrader: (0) Posts: 231 Rep Power: 17	A way to test injectors, remove rail to check operation, spray pattern and rate of flow. 4B-74/75 FSM 1988 F1-56 FSM 1990 Connector not on properly, think I mentioned that in a previous post. Common. Same issue I had with my GSL-SE. Except the plug was on fine but the wire was broken under the insulation. As I probed for signal an inch away from the connector it showed correct readings. When I took the connector off and tested it the signals were intermittent. When I pulled on the wiring the insulation stretched, found the problem. Two weeks ago had an FC that had intermittent running problems. On that one found a primary injector plug that wasn’t clicked on. He would hit a bump and it would start running bad, hit another and it would run fine. Had some other issues like fuel around injectors so had to replace all of the injector seals and orings. After replacing them and making sure all injector connectors were on it starts and runs great. We were also getting air past the injectors before replacing rubber. This was on a factory car that had never had to have any work done under the manifold. So it came from the factory this way. Amazed that it ran fine all these years. I was going to condemn the water temp connector (have seen plenty of them) because I could get it to run good or bad by playing with the wire, what I was doing was moving the injector wire at the same time. But couldn't tell it was injector until I pulled the manifold. Did not expect to find it not on completely. This is one thing I have found on working on cars all this time, most running or starting issues are related to a missing or bad ground somewhere or one wire mucked up somewhere. Especially after an install where the vehicle was running before any work was done. This is based on working on factory platforms. When wholesale changes have been made all bets are off. But still comes down to comp, fuel and fire. The FC3S is especially finicky with proper voltage and ground issues they are electronically overloaded as far as I am concerned. If they drop below 10V during cranking you will have starting problems flooding in particular. The ignition system really needs over 10v during cranking to give good spark. The motor also needs to be spinning fast enough. If it is 200rpm or less you can have starting problems, especially if compression is marginal. Having a multitude of little problems ranks up there with something that has not been taken care of for a long time or someone else that is not familiar with it has done the work. I have seen my share of those. Have a turbo buggy in here now that was one of those. Mostly age and vibration related failures. Previous owners just drove it hard and put it away hot. (Not the 2 seater that is shown on the website) Check and double check everything when you put the thing back together. Slow down to go fast. Also recommend sober and fresh. Congrates on finding it. Last edited by rx4ur7; 05-12-2009 at 01:22 PM..

05-12-2009, 01:29 PM	#32
vex RCC Loves Me Not You Join Date: Jul 2008 Location: Influx. iTrader: (6) Posts: 2,113 Rep Power: 19	For more clarification, this wasn't the injector plug which you were referencing. This was a body harness plug close to the ecu which was only partially together. Good read though none the less. __________________ The Official FC Radiator Thread My Project Thread: Cerberus CCVT Virginia Rotary Group

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05-12-2009, 02:00 PM	#33
rx4ur7 Rotary since 1972 Join Date: Nov 2008 Location: Tucson iTrader: (0) Posts: 231 Rep Power: 17	Ah ha, Sorry about that then. Pretty much same thing though. There was one that I had that one of the wires had pulled out a little from the harness connector. Connector was clicked on and tight. That one had me going for a while. Enjoy your ride now.