Ok I once more have a couple of days to work on my project sa rx7 with complete wiring from an 88 t2 (kevin landers old car), jspec engine, 3inch turbo back, front mount ic, 3inch intake,720cc injectors ect. I have most of the wiring finished excluding the lights and wiper control harness. I am tring to get it started, it turns over fine but does not start. so I start checking the list, fuel pump has power and pumps. pull the leading plug wire and no spark! take the multimeter out and start testing. test the coils and both pass, test the cas it does to. so I think check the fuses and the ones under the hood are all good and all have power, I then check the fuses under the dash the 15a eng fuse is blown change it out and try it once more. it blows as the key hits start. 1)what is the most likly short to cause this? 2)would this short be most likly to cause the no spark? next I am testing the afm. if a component where bad it would show as a open wouldnt it?

 

The engine fuse should be an 80 amp fuse.

Edit: yeah, the main fuse is 80A
the EGI Comp fuse is 30A and the Eng Inj. should be a 40A fuse. I just looked under my hood and there are no 15A fuses in the engine bay fuse box.

 

the 15A fuse I see in the FSM for the ignition also goes to the fuel pump and EGI components...but you said the pump was working...this is for the turbo wiring harness, right?

 

the 15a fuse is under the dash not in the engine bay. all fuses in the engine bay are good.

yes the 88 t2 wiring complete front bumper to rear. yes the fuel pump is working. thats part of my confusion with tracing the short down. inprocess of testing the afm right now. what could be crossed

 

afm test good. anyway to check the ecu with a multimeter? will recheck the fuel pump wiring right now for shorting.

 

if you have access to the FSM wiring manual (and some spare fuses), start disconnecting the components that circuit goes to, then hook them up one by one till the fuse blows again, that'll be your culprit...I'm trying to track everything down in the wiring diagrams now, these japanese wiring manuals SUCK compared to the ones we use for aircraft- I guess they tried to make them easier for rookies & that's why they're confusing to me...

 

I have a computer eng degree from the mid 80s and I agree the way that these manuals are set up suck, in the same diagram some points are over simplfied and some are drawn out.

 

back to basics- easiest way to find a short on a chassis grounded vehicle/ aircraft/ etc...is to isolate the sucker that's causing the problems- If you can't figure it out from the FSM, just start pulling connectors on anything that MAY be causing it...

 

I will post an update on this thursday thanks

 

the relay under the dash is what is causing the fuse to blow. anybody have a spare or can I get around this relay? it looks to cause a voltage drop from the fsm, and would this cause the no spark issue?

 

the relay under the dash is what is causing the fuse to blow. anybody have a spare or can I get around this relay? it looks to cause a voltage drop from the fsm, and would this cause the no spark issue?

 

https://www.rx7club.com/forum/attach...postid=1398836

The Circuit Opening Relay ..............provides a circuit to make the fuel pump work, depending whether the afm ground switch for the relay is *making* or not and whether the key is held to START or not.

So your saying if you pull that relay the fuse does not pop?

Did the fuse pop only when you went to Start? or just by turning the key to ON?

 

only at start the fuse pops. I unpluged everything on that circuit put in a good fuse then started pluging conectors in and turning the key to see what was causing the fuse to blow. it poped when I pluged in that relay after I turned the key to start.

 

This is tooo confusing for me. You say the fuel pump pumps? That can't happen unless the Circuit Opening Relay is pulled in. It gets pulled in by the power from the ENGINE fuse. So how can the Circuit Opening Relay be bad? Can't. Either that or the fule pump is rigged to run some other way.
I decided not to hurt my haid anymore. If the pump is wired *special*, then I'd think about it some more.

Do you have that fuel pump relay/resistor installed? The one that is installed somewhat in front of the afm?

If the key is to ON, and you go over there and push the vane in the afm back, does the fuse pop? Does the pump run when you push the vane?

 

I will try that

 

ok I opened up the relay and I am sure that its a problem. from looking at the guts of it, its the wrong one.

with the exception that I have a inline pump instead of intank, it is wired as the fsm shows( to the plug for the fuel pump).

the fuel pump relay/resistor is installed by the afm.

would this relay being the wrong one cause the no spark at the plugs issue?

 

As you can see from the schematic https://www.rx7club.com/forum/attach...postid=1398836 if you blow the 15 amp ENGINE FUSE, then there is no way for the MAIN RELAY to feed 12volts to the coils.

I'll take your word for the relay being the wrong one etc, but the mention of a different fuel pump makes me wonder. When you go to START, the Circuit Opening Relay pulls in and then feeds the pump from the ENGINE FUSE. If the new pump is wired wrong or is pulling tooo much amperage......POP goes the weasel!

 

If you had not taken the relay apart.....I would have suggested removing all the wires from the new fuel pump and then going to START with the key and seen what happened.

 

can I jumper the the conector for the 12 volts to the fuel pump resistor, and jumper the conector for 12 volts to the air flow meter or is the air flow meter to get lower voltage? it looks like it may from the diagram.

the fuel pump is the carter P70199 that is an upgrade replacement for the 84-85 rx7 gslse and several other fuel injected cars from 84-92 that used a inline pump. I do not have the current draw chart for it but I do not think it would draw a larger amount than the stock one for the t2. it is sopost to flow more fuel than the stock t2 pump though.