ok So here is my situation. I pulled the intake off my B21FTI to replace the pcv valve, and found most of the wires to be bare.. it was so bad i moved the harness and the starter kicked in! So anyways.. i re-wire everything and it is all back in much better shape.

I go to start it.. turn the key to the #2 position expecting to hear my intake pump buzz.. and nothing. Turn the engine over and sure enough, it doesn't start. So i begin looking for what it may be.. (thinking i forgot to connect something..) but everything checks as being ok.. i don't think i could have done anything wrong so i don't want to pull the intake off again to re-do everything. After i go back and try to start again the main ful pump fuse (#7) blows. Only when i try to start the engine. Still no in-tank fuel pump noise either. I figure all my grounds are good, so i am lost. Tried another fuel pump relay out of my parts car.. does no good. I read 12 pages of posts on the brickboard and found one other similar post. It was determined to be a shorted out oxygen sensor heater element. Could this be my problem? My ox sensor is located in the downpipe.. and it's just a 1 wire sensor, so i am unsure. From what i have read if i jump a wire from #5-#7 my in-tank pump SHOULD run. So that's one thing i have left to try, but still why the blown fuse, is this due to a bad oxygen sensor?

The car ran fine when i parked it, so i am doubtful in the fuelpump being the cause.
Does anyone have any suggestions to what i can try? I just did an engine swap in this car, went from a b23E to B21fti.. but my old fuel system has worked with this engine up until now (i guess the only thing that stayed was the in-tank fuel pump, the rest of the wiring harness was completely switched).
I need help, i miss my volvo!

Well i finally got it up and running again. I ended up pulling the intake off, checking a connector that i had removed from a k-jet car (because the wires were in good shape) and realized the blue and black wires coming from it are opposite. Who woulda thought the sanme connector and wires with the same color outa one car would be opposite to another. It was the plug coming out of the fuel pressure regulator.

The only problem is i think i messed up an injector when i replaced the seals.. as #4 cylinder has spark but doesn't fire. Oh well sooner or later it will be up and running.

Thanks for all the help guys, i certainly learned alot about the fuel system after this mystery!

...from what I (think) I know, I don't understand why reversed wires at the regulator would be a problem, since they are just for a heating element-- which doesn't care which way the power flows.
Seems like all you had was voltage going "backwards" thru a resistor--not going to ground (where it would blow the fuse).

Now I'm going to lose sleep till somebody straightens me out.
--
Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified)
New 144 from '67 to '78
Used '62 122 from '63 to '67

...that it is possible to switch wiring plugs between the Frequency Valve (the thing with a fuel line coming from each end, connected to the Fuel Distributor) and the Control Pressure (or Warm Up) Regulator (where you found wire colors reversed).

I know because I did it. And toasted the FV in short order, after running totally rich for a few hours.
--
Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified)
New 144 from '67 to '78
Used '62 122 from '63 to '67

Just went through the same thing on my 82. Installed a new engine wiring harness. Put it all back together, turned the key, ran for 2 seconds and stalled. Fuel pump fuse blown. After a couple hours of scratching my head and looking at wiring diagrams, I discovered I had inadvertently mixed up yhe conectors for the constant idle system temp sensor and the control pressure regulator. Reversed the conections, put in a fuse, presto.

You need to measure the currents to each pump and the Lambda unit to determine which is drawing to much current.

Update. I jumped the #% and #7 and sure enough. The fuel pump kicked in! I tried starting it and it ran for 1-2 seconds. (i did not continue to jump the fuses.. so i expected it to run for 1-2 seconds)
So now the problems

Why does the main fuel pump fuse blow
Why do i have to jump the fuse to get my in-tank fuse to run

1-Why does the main fuel pump fuse blow
2-Why do i have to jump the fuse to get my in-tank fuse(pump?) to run

1. Disconnect the O2 sensor if you suspect it, as you said in the top post.
Follow the black wire fron the sensor to where it connects to the green ECU wire. If the fuse doesn't blow now, the sensor must have been shorted.

2. Forget the intank pump for now. It won't cause a starting failure (with gas in the tank and a good main pump. Lets go thru what "should" happen when you crank it over...

A). Pulses from the ignition circuit "allow" the Fuel Injection Relay to "pick", (assuming Fuse 7 is good). The FI Relay then has 2 outputs:

B).Terminal 87 leads directly to the Main Pump, and also feeds Fuse 5, which leads to the Tank Pump. (So when you jumpered 7 (hot) to 5, you bypassed the FI Relay and put power to both pumps. AND ITSTARTED!
So I'm thinking the problem is a failure to pick the FI Relay

C). Terminal 87B powers the "Lambda" Relay and ECU, but that stuff is secondary at this point. I 'll post this now and check back.



--
Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified)
New 144 from '67 to '78
Used '62 122 from '63 to '67

I just went though a dash rewire myself and I would suggest you check your connections. I had what ended up being a bad ground in the one wire I didn't replace.