NEED HELP: 1974 1.8L Will Only Start with Brake Clean, Runs with AFM disconnected only Options

[Nor.Cal.914]

Hello everyone,

I have a 1974 1.8L that needs a new fuel pump and the customer purchased this pump from Pelican:

https://www.pelicanparts.com/More_Info/0439...59&DID=4630

I have already figured out the line routing in terms of inlet and outlet, but I do have a few questions about some other aspects. Being that the stock pump is a 3-port pump, first question is, what was the reasoning behind the 3 ports instead of just an inlet and outlet? My first thought was maybe an internal FPR, but I see there is a one in the engine compartment so that doesn't seem to be the case, but please correct me if I'm wrong! Second question involves mounting the pump. I have a 1975 so I'm not as familiar with how the 1974's were setup. This car has the coil style ring bracket around the pump which I'm now trying to figure out if I can utilize to mount the new pump. Main issue of course is the fact that all 3 lines came out on one side of the factory pump, whereas this pump has inlet/outlet on either side.

So my question is, what have you guys done to mount your pumps either in the same location or where did you place it instead of the factory location? Thank you in advance for the help! (IMG:style_emoticons/default/beerchug.gif)

-Christopher

[wonkipop]

here is what i think.

a few us here with 1.8s have established that an L jet with its fuel pump wired as per factory original set up will not run with the AFM disconnected.

reason. fuel pump is activated when the ignition is cranked to start - note cranked not just ignition to on. after the engine fires the AFM takes over. the flap will be moved very slightly and activate the fuel pump contact in the AFM unit. the dual relay fitted to the battery tray support on the rhs of the engine bay is part of the equation.
those with heads around electrical can tell you the why and the how.
but thats how it works stock.

hence fuel pump will not run in a stock wired fuel pump set up unless the AFM activates it after the cranking phase. if AFM is disconnected with its plug out it cannot run the fuel pump.

usually the engine will fire initially then pretty much immediately die within seconds if the AFM plug is out. this is how mine behaves. i still have factory stock set up of fuel pump operation.

the whole idea of the L jet fuel pump set up is safety. ie in a crash. engine usually dies/
fuel pump switches off. lowers risk of a dangerous fire with trapped occupants.

-----

now many L jets over the years have had the fuel pump either moved (to front trunk location) or replaced in stock location and have been wired to run when the ignition is in on position. no matter what. hence will always supply fuel regardless of AFM being connected or not connected.

in this sceanario, with the AFM unplugged the car will start and it will idle.
usually slightly elevated. say at 1200-1400 seems to be the usual experience.
if left alone the idle will continue to elevate slowly. it will rise and rise.
gettng to somewhere in the 2000-3000 range. after a few minutes it will die on its own.
but it will run. and you can probably keep it running the way you have with extremely tender throttle inputs. but basically it will not run in any thing you could describe as a satisfactory way.

what you are describing seems to fit this scenario.

ie your fuel pump has been wired to run all the time.
and hence will run without AFM connected. sort of run that is.


---------

so the real problem is with the AFM connected it does not what to fire.
doesn't even want to catch on cranking and at least initially fire let alone continue to run.
i am not sure what exactly that might be causing that.
i have a couple of L jet trouble shooting manuals and can look them up.
see what i can find.

in the meantime some other L jet owner might be able to input here with their suggestions.

if you post a couple of photos of the engine bay that might help.
try and cover all the top of the engine so we can see if anything is obviously missing or disconnected.

--------

in summary what i am saying is i think that it starts on fluild and runs with the AFM disconnected is what we in australia call a "furphy".
you can look that up on google.
don't be distracted by it. its meaningless that it runs in that way.
although it does prove its got spark.
and its got fuel. so its not that.
and maybe not ECU.

your problem is with the AFM connected it does not want to start at all.
this is the REAL problem.
so its AFM?
CHT (cylinder head temp sensor)?
or maybe the dual relay?
or the EFI wiring?
as with all things EFI it will be a matter of methodically testing and checking each component and the wiring.

its also possible your cold start injector is not working.
usually they will fire off that and run briefly off the fuel it provides at cold start.
but you are starting off brake fluid or other starter fluid. so......

i doubt its any kind of vacuum leak, since it will run with the AFM disconnected.
usually an L jet will not run at all with a vacuum leak.

[Nor.Cal.914]

here is what i think.

a few us here with 1.8s have established that an L jet with its fuel pump wired as per factory original set up will not run with the AFM disconnected.

reason. fuel pump is activated when the ignition is cranked to start - note cranked not just ignition to on. after the engine fires the AFM takes over. the flap will be moved very slightly and activate the fuel pump contact in the AFM unit. the dual relay fitted to the battery tray support on the rhs of the engine bay is part of the equation.
those with heads around electrical can tell you the why and the how.
but thats how it works stock.

hence fuel pump will not run in a stock wired fuel pump set up unless the AFM activates it after the cranking phase. if AFM is disconnected with its plug out it cannot run the fuel pump.

usually the engine will fire initially then pretty much immediately die within seconds if the AFM plug is out. this is how mine behaves. i still have factory stock set up of fuel pump operation.

the whole idea of the L jet fuel pump set up is safety. ie in a crash. engine usually dies/
fuel pump switches off. lowers risk of a dangerous fire with trapped occupants.

-----

now many L jets over the years have had the fuel pump either moved (to front trunk location) or replaced in stock location and have been wired to run when the ignition is in on position. no matter what. hence will always supply fuel regardless of AFM being connected or not connected.

in this sceanario, with the AFM unplugged the car will start and it will idle.
usually slightly elevated. say at 1200-1400 seems to be the usual experience.
if left alone the idle will continue to elevate slowly. it will rise and rise.
gettng to somewhere in the 2000-3000 range. after a few minutes it will die on its own.
but it will run. and you can probably keep it running the way you have with extremely tender throttle inputs. but basically it will not run in any thing you could describe as a satisfactory way.

what you are describing seems to fit this scenario.

ie your fuel pump has been wired to run all the time.
and hence will run without AFM connected. sort of run that is.


---------

so the real problem is with the AFM connected it does not what to fire.
doesn't even want to catch on cranking and at least initially fire let alone continue to run.
i am not sure what exactly that might be causing that.
i have a couple of L jet trouble shooting manuals and can look them up.
see what i can find.

in the meantime some other L jet owner might be able to input here with their suggestions.

if you post a couple of photos of the engine bay that might help.
try and cover all the top of the engine so we can see if anything is obviously missing or disconnected.

--------

in summary what i am saying is i think that it starts on fluild and runs with the AFM disconnected is what we in australia call a "furphy".
you can look that up on google.
don't be distracted by it. its meaningless that it runs in that way.
although it does prove its got spark.
and its got fuel. so its not that.
and maybe not ECU.

your problem is with the AFM connected it does not want to start at all.
this is the REAL problem.
so its AFM?
CHT (cylinder head temp sensor)?
or maybe the dual relay?
or the EFI wiring?
as with all things EFI it will be a matter of methodically testing and checking each component and the wiring.

its also possible your cold start injector is not working.
usually they will fire off that and run briefly off the fuel it provides at cold start.
but you are starting off brake fluid or other starter fluid. so......

i doubt its any kind of vacuum leak, since it will run with the AFM disconnected.
usually an L jet will not run at all with a vacuum leak.

wonkipop,

Thank you so much for all of the information! You've been very helpful already! I finally got back onto this car and put a fuel gauge in line to see what I'm working with. I found that with KOEO, there is no pressure, but will build to about 68 PSI when cranking, which seems like it is still wired properly in terms of not running all the time. The engine sputters occasionally with the AFM disconnected, but still won't start on its own and doesn't even attempt to sputter with the AFM connected. By any chance, were you able to locate the L jet troubleshooting manuals? I'm not exactly sure where to go next at the moment. If the dual relay was bad, would it still build fuel pressure when cranking? I wish I knew more in terms of how to test these systems, but any sort of guidance, flow chart, or wiring diagram would be incredibly helpful! I will have to look at my manual when I get home tonight as well to see if there's something in there that I can use. Thank you all for your input so far, I greatly appreciate it!

-Christopher