For years now I’ve use this form to work on my 78. Unfortunately I’ve been sick for the last couple of years and now I have a new LIVER and want to get the 78 back on the road.

Read everything I can find on the form about fuel pump systems I can fine.

 

So here’s what I’ve done.

 

1. Drained old fuel.

2. Remove all old fuel lines with new ones.

3. New fuel pump.

4. Replace all fuel filters,in front of the fuel pump, in before the fuel rail.

5. Replaced fuel rail with new Pallnet rail.

6. Brand new injectors.

7. Car will start with starting fluid and run for five seconds.

8. No pressure at fuel rail.

9. Removed fuel lines from filter before fuel rail and fuel pump pump fuel.

10. Blown compressed air into return line until fuel comes out of filter before fuel rail. (Clear)

 

Have bypass the oil pressure switch for all of these test.

 

If anybody has any advice I sure would appreciate it.

 

 

 

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 So the Bosch fuel pump, I spoke of is the Bosch 0580254044 fuel pump,  i’ve read they had a lot of the Z guys use this pump.

I’ll check the resistance on the pump tomorrow. Thanks for all your help any other suggestions always welcome.

Edited October 29, 20186 yr by Yellow78

Checking the resistance of the pump is not what I am talking about, its the resistance in all the wiring including the relay that supplies the pump with current. You need to check the voltage at the pump terminals while its running. Just make sure it does not drop too much (it will drop some compared to when the pump is disconnected, you just don't what a LARGE drop in voltage.

So it is definitely the pump is not pumping up to adequate pressure. I’ve done electrical test with a pump under load and I get less than
.02 voltage drop on the positive side and .005 on the negative side.

So I’m thinking that BOSCH 69136 would be adequate pump for my 280.

Has anyone used the BOSCH 69136. On Amazon for $74

Any feedback would be appreciated.


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Seems much more than adequate.  I don't know why they don't just put the specs out there somewhere.  That pump is a replacement for Ford F350's with 445 CI diesel engines.  Which means high volume of a more viscous fuel.

The general spec for a stock L6 is about 30 gph at 36 psi.  Higher volume means bigger draw on the electrical system.  You don't want that on these cars, the electrical is on the weak side already. 

The Airtex E8312 is a common replacement.  I have one, it's worked great for years and many miles.

https://www.amazon.com/Airtex-E8312-Electric-Fuel-Pump/dp/B000DT7Y7K/ref=sr_1_1?ie=UTF8&qid=1540865716&sr=8-1&keywords=airtex+e8312

 

Here's the data for the 69136 - 

https://www.summitracing.com/parts/bch-69136/applications

That’s the one I got on there now they had only pump up to 26 PSI. Maybe I just got a bad one.


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Is it new?  Pumps do go bad if they get crud in them, or rust up.   I had a wrecking yard pump that seemed fine in the first few minutes but would slowly lose power and pressure as it ran.  Even with the fuel cooling it the motor got hot and crapped out.

It's still unclear how, exactly, you're testing the pump.  Would love to see just a pump, some hose, an FPR, and a pair of pliers for pinching the return line.  With a gauge reading of course.

You're probably going to find that it was something simple once it's done.  Carry on.

11 hours ago, Yellow78 said:

So it is definitely the pump is not pumping up to adequate pressure. I’ve done electrical test with a pump under load and I get less than
.02 voltage drop on the positive side.

 

that seems odd, I would have expected more of a drop than that. That pump has to pull a few amps easy, with all the wiring and relay I would expect a bit more. Not a lot but more than .02v. Are you sure you are getting a good fuel supply to the pump? . I am going to take a reading later today on my setup and see what I get.

Maybe a current draw test would be a better idea. could do right at the battery. Pull the start solenoid, disable the cold start, ign to on, get a current reading, then to start get another reading. I will try that as well, give you something to compare to. Or I will just get a current reading right at the pump, that is better, but means having to disconnect one of the pump leads.

You could always just buy the OE pump they are out there, expensive but that should eliminate the issue. think it you shop around you can get them for around 200$ I replaced my working setup just to take advantage of the built in pressure relief the OE pump has. But still the after market pumps should work. I too had one of those airtex and it worked fine.

 

Edited October 30, 20186 yr by Dave WM

ok reading the amperage at the battery (start solenoid off, cold start injector unplugged) when switched to "start" to energize the pump was a fail, over 10 amps meter would not read, so no idea of what it should be. But if you want you can duplicate and at least confirm you are over 10 amps. Will try for a voltage drop at the pump later with my helper around.

Edited October 30, 20186 yr by Dave WM

Yes  it is new . I holds pressure fine at 26PSI  To make sure I was doing the check correctly I watched this video.

 

 

So just to be sure, you ran a wire all the way back to the pump and connected from the pump terminals and then compared to the battery post?

Yes yes just like the video. 

I get a 2.0v drop video to follow.

I also checked by leaving the setup but rather than look for  drop (pump + term compared to Batt + term) I connected from Pump + to chassis ground. got about 10v suppled to the pump. This is with the engine not running. Typical battery voltage with the alternator working would be close to 14v so a 2v drop would supply the pump with approx. 12v.

 

Edited October 30, 20186 yr by Dave WM