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Old 01-23-2010, 06:47 AM   #1
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Question How to add a lower cost inline fuel pump?

What are my options for a mod to add an inline fuel pump to an '87 LE Vin 3? Where and how could one safely add such a pump in the vin 3 engine compartment?

My reason for asking about a mod would be to lower the repair cost of installing a new in-tank pump at about $200 labor + $100 parts. My in-tank pump is weak at 29 psi tested at the shop'* room temperature. I'm told that normal is 34-36 psi. Currently it primes and starts normally above 30F. It apparently pumps too slowly when trying to crank in the 20F range.

The least expensive aftermarket inline electric pump "Universal Cube" is $45 http://shop.ebay.com/i.html?_nkw=IN-...&_sop=15&_sc=1
, but it generates only 6-9 psi for carbureted vehicles. The next part upscale pumps 85 psi, at over $100, but I don't need that much pressure for that price. Is there an inline pump available in between? For my need, would the "Universal Cube" be enough to get the car started when the temperature was low?

This company sells inline pumps stated for my purpose: http://www.inlinefuelpumps.com http://www.inlinefuelpumps.com/image...ump-design.jpg However, rather than a kit, these appear to be customizing parts with installation labor cost that could erase any savings over a conventional repair. Is there an available kit anywhere?

Thanks in advance,
Jim
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Old 01-23-2010, 12:44 PM   #2
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Your intank pump will die eventually overloading the inline pump and causing it to die prematurely. If the line curves down to the mounting point for the inline pump, the inline pump may lose its prime, cheap pumps (and even Walbro pumps) will be destroyed by running dry. This will leave you out money, time and possibly with a car that is stranded somewhere.

GM Parts Direct has your factory replacement pump for $75~$150 depending on the part number.

Rock Auto has a complete replacement kit for less than $60

By the time you buy:
  • good pump ~$100
  • Fittings and wiring harness ~$40
Both options are above are cheaper than an inline band-aid, with factory reliability and quality.
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Old 01-23-2010, 04:37 PM   #3
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Just buy the pump yourself off ebay, a intank pump. Do it yourself and be done with it. Just drop the 2 bolts on the tank straps yourself, they maybe be rusted and then there'* a retainer ring on top of the sending unit and just use a flat head screw driver and a hammer and hit the bigger tab in the unlock position and then pull it out and change the pump. Be very careful not to smash the sending unit or bend the rod. Let me know what kind of car you have exactly and ie make, model and engine size. I have a fuel pump here, I just would want to make sure it fits. If it does, I will take 35.00 for it plus 10.00 for shipping and its all yours. If you can't fix it yourself, take the pump in with the car to the shop. It will be a little cheaper atleast. Shoot me a pm or something.
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Old 01-23-2010, 04:39 PM   #4
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Old 01-24-2010, 07:55 AM   #5
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Thanks for the replies, and lower cost sources and offers. I also appreciate the how-to tips. The commercial repair manuals rarely suggest how hard a job may be.

There are others interested in doing this inline pump mod, but those knowledgeable seem to agree that it'* ordinarily not worth doing. See http://wiki.answers.com/Q/Can_you_by...an_1500_series

Doing the in-tank pump replacement myself certainly would be the way to go, and I would try if they would let me. Unfortunately, I have a gigantic national corporate landlord, street-only parking, and a lease that specifies eviction for not having matching window shades (seriously), much less getting caught working on a car. The local management is right across the street watching.

My long-time regular auto shop is within walking distance, and the mechanic has done a lot of extra stuff for me for free, so I want to keep him happy. He said the in-tank pump replacement is not a job that he wants to do. So it'* going to be a higher labor cost by someone I don't know, they might refuse to allow me to supply low cost parts, plus my transportation to and from somewhere, add $20-40. Right now, the job is commercially unaffordable for me. I don't expect you folks to solve my personal problems, but I wanted to explain why I'm trying to find a low cost band-aid fix that will keep me driving, even if it'* not the best way.

> pumps will be destroyed by running dry.

I thought that was a bench test or troubleshooting issue. Maybe it was only an expensive pump I saw that could run dry for 5 minutes. I assumed that the car would quit running long before the pump could be damaged after installation.

> the inline pump may lose its prime

I hoped that an inline pump with adequate suction in and pressure out could simply take over for the in-tank pump without a replacement. I don't know anything about the construction of electric fuel pumps. Not all pumps are constructed this way, but classic water pumps that quit working have free-swinging flap valves that simply open when another pump is placed in series. Flap valves shouldn't cause enough fluid resistance to overload the downstream inline pump.

If the in-tank pump has flap valves, even a cheap inline pump shouldn't be overloaded. However, I suppose that 9 psi won't be adequate for fuel injection after the in-tank pump quits. Would the engine sort of barely run at 9 psi? If not, what'* the absolute minimum psi for smooth idling?

Also, can you clue me as to pump operation and wiring? Does the in-tank pump run continuously or on demand from a built-in pressure sensor? My mechanic showed me how to listen for the 2 second priming run after keying the ignition on before cranking. Is that 2 second prime done with a separate wire from the ECM, ICM, or wherever?

One of the things I can try during the next 20F cold spell is to repeatedly key the ignition on before trying to start, until the pump heats up enough to prime.
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Old 01-24-2010, 10:51 AM   #6
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The wire to the pump is just 2 wires, 1 (+) and 1 (-). The other wires going into the sending unit are for the ohm wires based off the sending unit float level in which change your gas gauge to full to empty. If I'm understanding you correctly you have a low pressure problem and wanna run the inline along with the current pump to boost your pressure to the normal rate. I guess you wanna run both pumps at the same time? Well, what will happen is that your in tank pump is making more pressure currently than a low pressure inline would be, so what would happen is that the inline wouldn't do anything at all. It would actually hold back pressure and restrict it even more. First of all, all that a shop would do if you brought your own parts at the worst is state they won't put a warranty on the job. Even though if you bought a fuel pump from them, they would say its warrantied. They are right, so if it does go bad, they will warranty the parts, but still not the labor. So either way you will pay for the labor if it ever fails again. If your wondering which wire going to the fuel pump is positive, then find your fuel pump fuse, usually on the older models its a seperate fuse with just a cap on it under the hood between the back of the motor and the windshield side of the fire wall. If you can see the wires below the fuse and take a look at the colors of the wires. Then look at the wires going to the top of the sending unit on top of the fuel tank. Match the 2 colors up and then you will find your positive source wire. Fuel pumps actually use gasoline as there lubrication source. The only other way to solve your problem is to drop the tank, remove the old fuel pump, and run a piece of hose in place of it and eliminate it completely and then run a high pressure inline pump. But then again, replacing the in tank pump is alot easier. As far as your pressure regulator question. Yes its a built in pressure regulator. Right on the fuel rail where the fuel injectors are found there is a round fuel pressure regulator. That regulates the pressure, a quick way to test it, to see if its bad, is to start the car, let it run for a few minutes, rev it up a few times and shut it off. Then pull the vacumn hose off the top of the regulator and see if you see any gas. If you see a drop of gas in the vacumn hose then you know the regulator is the problem.

Did you change the fuel filter yet? I seen plugged filters limit flow and make a car not want to start. I just did one on a 2000 bonneville. It didn't wanna start when it was also below 20 degree'* out. It ran fine under full throttle. But it was also really low on fuel pressure. I would start with a fuel filter. Then go from there. I'm pretty sure the pump I have would work for you, just call and ask your shop if its ok.
thanks
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Old 01-24-2010, 11:03 AM   #7
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I had a pump go out on a car of mine, and I had a spare as well. This was on a 89 chevy beretta, but I had a apt at the time and I just pushed it out onto the street parking area, and I went and bought a set of car ramps and jacked it up and put the car ramps under it, and I changed it out on the street. I understand your management maybe across from you, but they can't evict you or do anything thats done out on the street as thats city. I am currently going threw a problem at my cousins house where the neighbors are spacing there vehicles apart just far enough so there friends have no where to park. I called his landlord personally and he also even stated that its city property and he can't do anything about it. So its all up to you. I did my pump in 1 1/2 hours. With bare minimum tools. You can do it do. Plus it was raining out lol and I was getting all wet from the water, but crap happens lol. I needed a car for transportation so I had to do what I had to do.
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Old 01-24-2010, 11:17 AM   #8
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If you want to use a in-line pump here is a link to a 85 psi pump. Now your factory fuel pressure regulator will regulate it without a problem. So this is what you need. You will have to buy a piece of high pressure gas line from a carquest or parts store and cut some metal line out and just slip the hose onto the metal line and onto the end of the pump. Here is a link to the exact pump you need to get. http://www.summitracing.com/parts/SUM-G3138/?rtype=10

Now! You will still have to drop the tank, and remove the fuel pump and in place of the pump, you will have to run a piece of hose to the bottom of the sending unit and still find a way to have a filter/strainer at the bottom. Because the fuel pump in the tank is obviously used to push fuel not to be used as a suction pipe, I have heard of people leaving it in there just unhooked, but the problem is, since its not working and allowing the full potential flow of fuel, there lies a problem, your restricting the fuel flow to this new pump and that may cause failure.

So, by the time you find the wires powering the stock fuel pump and run them to this pump, your still using about the same time and money. I would just spend the money and get a pump off ebay or something.
Craig

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Old 01-24-2010, 11:25 PM   #9
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> If I'm understanding you correctly you have a low pressure problem and wanna run the inline along with the current pump to boost your pressure to the normal rate.

Close, but not exactly. The Bonne currently runs except for non-starting at 20F. I was hoping for the scenario in which a new low-cost low pressure inline pump either adds 6-9 psi, or does nothing unless the in-tank pump fails. 6-9 psi might get me started at 20F, and maybe let me limp home when the in-tank pump eventually fails completely. That'* why I asked what the minimum fuel pressure for a smooth idle is.

> 2000 bonneville. It didn't wanna start when it was also below 20 degree'* out. It ran fine under full throttle. But it was also really low on fuel pressure.

Did you get a psi gauge number on that really low fuel pressure?

> Did you change the fuel filter yet?

Yes, my mechanic did that last week in case that was causing the low pressure. It wasn't.

> drop the tank, remove the old fuel pump, and run a piece of hose in place of it and eliminate it completely and then run a high pressure inline pump.

I don't think removing the in-tank pump is necessary, because Walbro http://www.inlinefuelpumps.com advertises:
"Walbro inline fuel pumps are ideal fuel pump replacements and upgrades for:
- Vehicles with expensive or hard to replace intank fuel pumps."
This ad implies that OEM in-tank pumps have valves that simply open up when an inline pump is placed in series.

> I understand your management maybe across from you, but they can't evict you or do anything thats done out on the street as thats city.

Alas, their gigantic national corporation no-repair rule also applies to the city street. It'* obey or leave, and I can't afford to leave. (I didn't choose them, the old local owner sold out to them and retired.)

> your in tank pump is making more pressure currently than a low pressure inline would be, so what would happen is that the inline wouldn't do anything at all.

In simple theory it should work, but depending on the pump'* construction you could be right.

Two identical pumps in series should add their pressures the way that two batteries in series add their voltages. But adding a low pressure inline pump in series might not work like high and low voltage batteries in series do. If the low pressure pump has input and output valves, the higher pressure in-tank pump might just hold both low pressure pump valves always open and thus no pressure would be added by the low pressure pump unless the high pressure pump failed (or got as weak as the low pressure pump).

> Fuel pumps actually use gasoline as there lubrication source.

If fuel lubricates the pump body, does it also lubricate the pump'* electric motor bearings? This illustration sort of looks that way: http://www.aa1car.com/library/fuel_pump.htm I was assuming that the reason for the 20F failure was that the electric motor bearings were running out of lubrication, and what lube remained was too viscous at 20F. But now I'm less certain of that. The only other clue is the somewhat low pressure.

> a round fuel pressure regulator. That regulates the pressure

Ok, I think I get it. The fuel pressure regulator activates the fuel pump relay whenever more pressure is needed in the fuel rail.

Is my fuel pressure regulator bad? I don't know. I assumed that my experienced mechanic attached his pressure gauge directly to the tank line and activated the pump until it maxed out at 29 psi. If so, this test would point to the pump rather than the regulator as the component that was likely to be the cause of a very difficult 20F start. But maybe he just connected to the fuel rail'* Schrader valve and was reading the regulated pressure? I just don't see how regulated pressure that was only 6 psi low would prevent starting only at 20F.
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Old 01-24-2010, 11:38 PM   #10
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Hook up the fuel pressure tester to the Schrader valve and turn the key to run, but do not start it. This should be unregulated pressure. Then start the engine, is the pressure about the same? Also, with the engine off, pull the vacuum line on the FPR and smell it, do you smell gas? If so, the diaphragm is damaged and the FPR is shot.
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