jpitman2

Safest way to do some of this testing is a length (10-12ft) of two core flex with male spade tags at one pair of ends, and a switch at the other. Plug the spades into the relay socket 30 and 87, then you can go to the test place - the pump, the return line etc - and readily switch the pump on/off QUICKLY. Check the volts at the pump with at least one of the leads disconnected from the external pump to see if you have +12V with no load. If it drops more than 1-2V under load, there is some sort of high resistance/load in there. Try to do this test with each pump separately to see if under load there is a difference in behaviour. If you have a big enough DC Amp range on your meter, try to measure current also, for each separately. We have a big 12V gel cell in a torch here, and unloaded looks great, but loaded falls to almost nothing immediately.
jp

jwillman

I did make a test wire per your description based on previous guidance provided on the list

I did not check voltage unloaded. I will try that tomorrow. Need to brush up on my multimeter skills. I have an idiots guide to digital multimeters also acquired on this site

Thanks for sharing the knowledge!!!!

Landseer

The ground for the pump is located under the back corner of the passenger interior quarter panel. Might be corroded, unless you already cleaned it.

Try measuring the hot lead thru the meter, to a body ground/battery. Should give 12V ish.

jwillman

Landseer,

I have not got to the ground point mentioned but will do that next. I have already replaced the battery and under engine grounds.

Thanks

jpitman2

Yes, as Landseer says, a bad ground for the pump could give the symptoms you see, so I would test that next on the list.
jp

jwillman

So went from the power terminal at the pump and ran a wire to the battery ground in the hatch area. Checking continuity between power terminal of pump and the ground terminal gave me all 0000 or a good ground as I understand it. When power was turned on pump surges and I am reading the same voltage as before, fluxuating around 7.75 v. I still have battery voltage at pins 15 and 87 at the relay box.

Guess next steps are to run the wire between the connector at the relay panel and the pump for continuity and check the terminbals where between the connector and the relay panel? Any other ideas?

Landseer

Well, just one.

Back at the CE panel... fuel pump relay.

Its possible to have 12v on the socket to energize the relay coil (can be jumpered with 30 to 87 lead in absence of the relay). What is the out put voltage, then, of the pin that corresponds to the fuel pump hot lead?

I've had a situation where I had 12V actuating a relay, but due to melted wires on the back side of the panel, voltage was siphoned-off somehow and I had between 7V and 10V at the power output from the panel, depending on phase of moon.

You should have 12V ish at the pump. If not, there is a partial short somewhere I think.

First maybe disconnect the fuel pump hot lead and measure voltage at that end without the pump in the loop.

jwillman

Well I just tried that and snapped off the positive power terminal from the pump trying to get the nut off the post. The good news is after many choice words I checked voltage at the power wire and had 11.6v.

So seems power supply is good but now the pump is definitely bad.

What options do I have for pumps? I have read about higher output pumps. Any recommendations?

Should I be hearing noise from the in-tank pump?

jpitman2

I wouldnt bother with anything other than spec pump for your model - or any Bosch injection pump that wil physically install to the existing fittings. My CIS car had an S4 pump on when I got , no problems - CIS needs more pressure than an S4, but it worked fine. Later pumps may have different check valves - separate screw in unit, but doesnt really matter as long as everything its together and seals - new copper washers are a must. If you have +12v at the pump leads , and cant hear the in tank running (assuming you are down there under the tank, and you are not deaf), then I would guess its toast, AND its not dropping the volts either. It should give off at least an audible hum down there. While you are down there, can you check that the meter drops volts reading when you apply the + lead to pump post remains, being careful about sparks? This would tend to confirm the pump is stalled/jammed. Mine jammed on debris once, and reversing polarity briefly spat out the debris, and it ran for several more years.
jp 83 S

The connectors on the tank fitting are spade tags I thing, so should pull off. Its always possible some PO has disconnected the intank pump leads where they join the external pump leads, so its worth tracing the wires to check they are connected.

jwillman

So I have decided to remove the external pump and drainthe tank, drop the outside tank support so I can get access to the in-tank pump.

The banjho fitting is on way tight. I have sprayed it with PB. Since the pump is bad any way I am more concerned about the banjo fitting.

Any ideas or other gotchas for what I am going to do?

Thanks

Landseer

Just be safe.

jwillman

So I got the external pump out and am drainig the fuel. Fuel is a deep golden color. Not sure if it is old or if the PO put in some kind of gas treatment. Any ideas?

Fuel is also pooring out at a pretty slow rate. Is this because of the in-line tank pump or blockage? I expected the fuel to flow pretty quickly given the size of the supply line.

Any tips on taking out the in-tank pump?

Thanks

herman maire

I didn't know a 79 had any in tank pump..... I know on my 1980 that bottom hose feeds the fuel pump thats bolted to the fuel filter bracket. That is the only pump on my car.

After that, the only other thing is the fuel level gauge that you remove from the truck area. I am almost positive the pump on the fuel filter bracket is the only pump on your 79.

jwillman

Roger from 928rUs had conformed by VIN # that my car has the in-tank fuel pump in another string as I was confused as well, lucky me!

Once I get it drained and pulled I will post pic's.

Landseer

There was some discussion here once about dual fuel pumps being installed for cars delivered to regions with higher altitudes. Can't seem to find the reference, though.