fuel pump surging, why?? Options

[Dr Evil]

Wow! I am totally suspect of this engine now. I can't wait to see what the next turn shows us. If nothing else, you will learn a lot. (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

[Tab914]

Yeah! Learning alot about my patience.......... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

I found out from Gordon Luy that the heads are interchangeable though. Me thinks that someone took the engine apart for a rebuild or what not and when putting it back together switched the heads by mistake and only realised after most of it was put back together. I guess it was easier to punch a hole in the cooling tin and swap sides for the HTS then to tear down again and reswap the heads. Gord tells me that this in no way affects the HTS.
I did swap the sensor today and got better results. Brought the car up in temp to the usual spot and no surging. (wasn't as warm out today though) Did get some stumbling from the engine though. I didn't drive the car today and only brought up the temp from idling and steady revs of the engine. I got some engine poping and gurgling (burping, missing, whatever) at low rpms (1200-2000) on steady revs and acceleration. It seemed fine at steady higher revs (2500-4000)
Does that mean running a little rich or a bit lean?? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

Still plan on doing the fuel pressure test hopefully tomorow if not then the day after. Will also change fuel lines, filter and check screen in bottom of tank. Also fuel line to fuel pump and injectors. Will let you know of the fuel pressure and hopefully get more of your input.

Thanks again. (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[Tab914]

Ok. Well, as I am getting ready for what has now become my weekend project ( changing fuel hoses, fuel filter and checking fuel pressure to better inform you guys) I am going over fuel hose diagrams and notice that on all of them the fuel filter is in the front between the fuel tank and the fuel pump. It is set on the hose going into port "S' on the pump. On my car the fuel filter is in the back between the pump and the engine. It is set on the hose that is coming from port "D" on the pump. I am not sure how the return hose is set up i.e. the "Y" connector to split the fuel to the tank and to the pump. My question now is, can the fuel filter being where it is be problematic or is that a non issue? Also, on the diagrams, the fuel filter is shown having two different size ports. (7 & 9mm) I know that this is because of the different hose sizes but can you get away with a filter with say, two 8mm ports?
I would just like to clarify these issues before I start swaping hoses and finally checking the fuel pressure.

Thanks guys. (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[mihai914]

Dominic, you've got a major problem right there.

That would explain why the pump was changed before and why you will keep changing it unless you do things the way they were supposed to be done, correctly.

It is a must to have the fuel filter before the fuel pump. I reallly think now that you probably have loads of crap in the gas tank and occasionnaly it causes your fuel pump to work harder.

You can probably use a 8mm/8mm filter, it will just be tight to get on the 7mm hose.

I say don't rush the fix for the weekend, remove everything over the weekend, clean as much as you can.

During the week order a correct fuel filter and plan on reinstalling everything next weekend.

BTW you should leave the old filter where it is now as a second backup filter, there is nothing wrong with having two.

I'll try and find you a correct diagram for the relocation of the fuel pump.

[mihai914]

Here is the article and drawing I was referring to, no the best but the most common. My only complaint is the very tight spot up front for the fuel filter and the fact that an original filter is not well adapted to the hose change diameter.

[Tab914]

Thanks Mihai.

Like I said I only noticed now that this was not as it should be. I didn't do the relocation myself. (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif) I am getting a proper fuel filter tomorow but was only wondering about the 8mm filter. I realise the filter should be before the pump to keep crap out of there but is the filter being where it is now affect the fuel pressure or flow in any way?

Thanks. (IMG:http://www.914world.com/bbs2/html/emoticons/wavey.gif)

[mihai914]

QUOTE (Tab914 @ Aug 4 2005, 11:32 PM)

I realise the filter should be before the pump to keep crap out of there but is the filter being where it is now affect the fuel pressure or flow in any way?

No it doesn't, I have one up front before the pump and one in the original location before the injectors just for the heck of it and there is no problems whatsoever.

When you'll redo the whole thing, the sucky part will be to go from the D port of the pump which is 7mm to the center tunnel feed line which is 9mm, I used a 7mm id fuel hose but it was very hard to get it on the fuel line.

The reason to use the 7mm/9mm original filter is because the pickup at the fuel tank is 9mm and of course the S port at the pump is 7mm DUH! so the filter acts as an adapter. I wish I knew of a round 7/9mm filter as the square one takes alot of space under the steering rack.

Do whatever it takes to have a look inside the gas tank and see if there is junk there, and it's actually not that hard to get the junk out of there, getting it spotless is another story.

[Tab914]

Cool. I'll let you know how it goes.

[Dr Evil]

I actually had a problem with a fuel filter that was very similar to what you are experiencing. If the filter is the wrong size, or your pump a little waek the filter on the wrong side can act like a bucket rather than a continuous flow of fuel. It will show full pressure when the filter is full of fuel and then when you give it gas and the little filter resivoir depletes the pressure drops. I agree that you should take your time. There is always potential that there is more than one problem causing your symptoms. It usually, and I don't know why, is three.
$.02US

[Tab914]

Thanks Dr. Evil.

Kinda feels like I'm getting somewhere with this. Hope it will help in solving this problem. Leaving now to get all my stuff and, yeah I will take my time. Don't like playing with fuel. (IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif)

More to come.

[Dave_Darling]

Just to clarify, there is a filter with a larger inlet fitting and a smaller outlet fitting. There is also a filter available with small fittings on the inlet and outlet both. Those cars evidently used a special "converter hose" to go from the 9mm hard line to the 7mm inlet.

--DD

[bd1308]

1970-1974 8mm/8mm Fuel filter
1975-1976 8mm/10mm Fuel Filter

Locally there is a 8/10mm filter for sale.

[Tab914]

Well, today I gor set up to do the bulk of the work tomorrow. I did have time to check the fuel pressure and it was set at 36psi. So I brought it back down to the suggested spec of 28psi. The car doesn't idle as well right now though. (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) Does the fuel pressure affect in any way the timing and such?

Also, and I will probably get some flak for this, but I also finally got my hands on a vacuum pump and my MPS does not hold vacuum. SON OF A B......... (IMG:http://www.914world.com/bbs2/html/emoticons/mad.gif) (IMG:http://www.914world.com/bbs2/html/emoticons/headbang.gif)

Can you say $$$$$$$$$$$$$. I guess that that is the evil of all my problems right? Stupid question right? (IMG:http://www.914world.com/bbs2/html/emoticons/screwy.gif)

Now I am depressed. Feel kinda sick too (IMG:http://www.914world.com/bbs2/html/emoticons/barf.gif)

[Dr Evil]

You can get a used MPS from the guys on the left coast. I gave a few to them when I left. Don't lose hope. The fuel pressure does effect how your engine runs.

[Tab914]

Anyone with a spare (working) MPS for a 1974 2.0lt. willing to part with it at a reasonable price please pm me or email me at f_bbanffnorquay@hotmail.com.

Hope somenone out there has one. (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)

[mihai914]

QUOTE (Tab914 @ Aug 6 2005, 09:48 PM)

The car doesn't idle as well right now though. (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif) Does the fuel pressure affect in any way the timing and such?

High fuel pressure will mask very well other problems especially vacuum leaks. Once you find a good MPS and reset the air screw on the throttle body, if the idle still isn't good, you'll have to start chasing vacuum leaks if you have hunting.

When you say the MPS doesn't hold vacuum, how bad is the leak?

[Tab914]

[/QUOTE]High fuel pressure will mask very well other problems especially vacuum leaks. (tried to do the quote thing here but don't know how)

That's what I thought when I noticed the difference in how the car ran. The fuel pressure might have been set high to compensate.

As for the MPS it's not that it leaks it's that I can't draw a vacuum at all. I tried with a pressure pump and guage and nothing. Took the pump off and tried sucking on the hose and nothing. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) Couldn't get any suction on my tongue. Tested the guage and pump another way and it works. So me thinks it's screwed. Probably still good to knock someone out if I threw it and hit him in the head with it. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

Now the hunt for a replacement is on. (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)