sudden OFF of engine on freeway

[deeze30]

Ok i've been reading and searching about how to modify late model in tank pumps to work with early model but i cant seem to grasp the idea how? Is there any write ups anyone can link me to? From what i read is that, 1. you have to splice in a second sender from driver side but there's no hole there? Make one? And how exactly do you splice the second sender to the left sender? 2. What happens to the crossover fuel line coming from in tank pump/left side? 3. Does external pump go away if late model in tank pump is used? And 4. Some routing of fuel lines i dont quite understand?

please help. Its my only car and i have to borrow a car from someone for now for work until i get my car running again.

[packratbimmer]

Early cars had a low pressure pre-pump and an external high pressure pump. Late cars had one high pressure/high volume pump. They are not compatible.

[deeze30]

Early cars had a low pressure pre-pump and an external high pressure pump. Late cars had one high pressure/high volume pump. They are not compatible.

But from what i've been reading there is a way to modify the late pump to work with the early system?


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[packratbimmer]

Yes - it should be fairly simple. You would have at least one HOT wire to cap off after you eliminate the external pump - don't want that dangling around!

As far as the fuel level senders go, I think the senders depend on the tank so you are all set.

[deeze30]

Yes - it should be fairly simple. You would have at least one HOT wire to cap off after you eliminate the external pump - don't want that dangling around!

As far as the fuel level senders go, I think the senders depend on the tank so you are all set.

Okay so if I understand this correctly...(correct me if i'm wrong) You take the late model in tank pump/HP (cause it does both jobs for late cars) and drop it in the early to replace old one and splice harness because late harness connector has both neg and pos while early only had positive and grounded to pump/chassis, but how about the fuel return line for the early pump? do I just remove that tube altogether? Where does that tube go anyway? to Fuel filter then external pump? No need to cut a hole on my driver side back seat to gain access for a second sender? i'm just confused as to how the extra fuel line and external pump elimination works and to visualize how it'll turn out

[packratbimmer]

Sorry man - have not done that conversion. You will definitely need a return line and there are vent tubes involved. There must be a comprehensive write-up out there.

[deeze30]

I'm starting to believe it may be the CPS. Just from a lot of threads i've been reading with simialr issue as mines always ending up with the CPS as the culprit.

So far i've tested both in tank pump and high pressure pump by bench testing them and they both work, Cleaned all battery terminals front and rear. I've also jumped fuel pump relay 30 and 87 and tested relays with a 9v battery and they all checked out except when i jump 30 and 87 i get no response from the pump. Even if CPS was the problem shouldnt the pump power on by jumping it?

[StereoInstaller1]

No, because the fuel pump relay is turned on my the main relay, which controls power to 2 things: DME and fuel pump.

No power to either at the main relay is common, sometimes one works.

The fact that the CE light didn't come on is how I know it's not the CPS. Bad CPS, the CE light comes on. If you think there is any chance I am wrong, go unplug the CPS with the key on.

If you want a test, make a jumper between pin 30 and BOTH pin 87s on the main relay. Flip it over, you will see one red in, 2 reds out.

[deeze30]

No, because the fuel pump relay is turned on my the main relay, which controls power to 2 things: DME and fuel pump.

No power to either at the main relay is common, sometimes one works.

The fact that the CE light didn't come on is how I know it's not the CPS. Bad CPS, the CE light comes on. If you think there is any chance I am wrong, go unplug the CPS with the key on.

If you want a test, make a jumper between pin 30 and BOTH pin 87s on the main relay. Flip it over, you will see one red in, 2 reds out.

Okay i'll try that tomorrow. Silly question lol but How do one make a jumper for that? A wire with 3 end spade connectors pretty much? Would it hurt to check CPS and give it a little cleaning? I have a 2nd DME, i might try plugging that one in tomorrow and see if that does anything

[StereoInstaller1]

double jumpers? two short chunks of wire and 3 spade terminals, daisy chain style.

You can also just use 2 paper clips, but you need to make sure both 87s are powered.

There is just about zero chance that cleaning will improve a bad CPS.

[deeze30]

double jumpers? two short chunks of wire and 3 spade terminals, daisy chain style.

You can also just use 2 paper clips, but you need to make sure both 87s are powered.

There is just about zero chance that cleaning will improve a bad CPS.

is there anything else I should be looking into besides the ones I have already and this?

[deeze30]

well she's back guys :) found out what the prob was. Turns out i accidentally sandwiched the ring terminal that's connected for the fuse box onto the battery junction block when i cleaned the terminals... Haha (here's a example picture, not mines)



I'm still wondering what the cause of the sudden death of it on the freeway and the hard starts... Maybe it was just dirty terminals after all, we shall see... But thanks everyone for the help at least it gave me ideas what to check for for problems in the future :)



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[StereoInstaller1]

Hoping for the best, that wire runs damn near everything