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Hi, I'm starting work on my uncle's 1999 C5 I inherited. The car has not been ran for around 8 years so there is old fuel in it. I was going to run the fuel pump to drain fuel from the fuel rail but I've discovered the fuel pump isn't running (it's getting 12v at the pump multiplug). I guess it's shot. Not coming priming with ignition was first hint.
I'm in the UK so limited choices. I can get this Walbro GRJ420P 255LPH easily enough https://www.ebay.co.uk/itm/WALBRO-25...8AAOSw8HBZHDZZ
I have no experience of changing an in-tank pump. Should this Walbro be ok and is it relatively easy to swap? Do my circumstances of this car lying with bad fuel in it mean I should replace with one of these: Rock Auto have a SPECTRA PREMIUM SP6095M https://ecat.spectrapremium.com/products/SP6095M
I see the Spectra incorporates the sender and wiring etc. Would that be a better choice for me? I don't want to go crazy price wise especially as I am in the early stages of resurrecting this car and am still unsure how viable it is to see through.
The pump will only cycle for a quick moment if the car is not being cranked or running..
On a 99, I would pull the fuel filter first = you can kinda tell how bad the fuel is then too.
The filter IS the regulator, so only use an ACDelco or Wix Filter.
There is a way to "hotwire" the pump at the BCM, But I'm not the guy for that...
A friend and I swapped the fuel pump for the Carter drop in unit on his 2000:
Part Number: P74895M
Looks like the 99 may be another part.
The fuel level sensor was in bad shape. It wasn't a bad job but it is messy, try to do it with as little gas as possible in the tank. If you can't drain the tank be sure to be careful and have something to catch as much fuel as you can. I am glad we did the entire assembly. Seems easier and it was complete.
Lingenfelter has a nice set of instructions if you change just the pump
Thanks for replies. I jumper cabled the pins at the fuel pump relay first and all was quiet. I have now seen that there was however constant 12v at the pump itself. My fuel gauge was slightly erratic going up and down from almost empty to showing an eighth full (if anyone can shed any light on that please do?) so obviously not likely very full so thats good as far as draining is concerned (from the FP housing..). I will see if I can see the earth G401 for the FP. Behind the rear wheel, is it under the splash guard? Having said that my rear lamps were working (and fuel gauge other than it's erratic behavior) so I think the earth will be ok.
Where are you 93 Polo, Ireland? Looks like I can maybe get the carter pump but it's quite expensive.
Is the fuel filter regarded as quite easy to change, it looks like the exhaust is in the way!! Any opinions on the SPECTRA SP6095M from Rock Auto. Rock Auto seem a good place to get parts sent to the UK from but unlike everything else they're only offering two pumps!
Silver, if you seeing 12 volts at the fuel pump harness (gray wire) you also have to check the ground (G401)...it is located inboard of the left rear tire (picture enclosed) and is on the frame rail inboard of the rear part of the tire...I'd remove it and take some emery cloth or a wire brush to it...a visual inspection is not good enough. You can try jumping 12 volts and a ground directly to the pump and see if it runs...if not the pump is most likely bad !!...as far as the "earth" it's best to load test it with an old headlight bulb...when connected to battery positive and probing the ground terminal the light should come on bright indicating that the ground can carry the current !!...hope this helps !!
Thanks. Many thanks for posting the picture but I found the earth point when I looked earlier today. Mine certainly looks somewhat rusted up so I'm about to check it as final test to see if the pump is bad. I noticed when using mini jumper cables at the front end that getting a very good earth was essential and WASN'T particularly easy!
I was surprised the two gray wires at the fuel pump harness are plain gray. I'd have thought one might be (for example) gray/white for the fuel level sender. However the other two wires are colour coded, which are obviously the grounds. Yes, I perhaps should just pop a fused 12v supply directly to the pump.
Last edited by silver50; Nov 22, 2019 at 08:01 AM.
NO problem !!...yes, there are 2 gray wires...one for pump and one for sender and black is pump ground and dark blue is for sender...pin A (gray) is pump power, pin B (gray) is sender, pin C (dark blue) is sender, and pin D is pump ground !!...I did a YouTube video on checking the pump relay circuit if you need it and is enclosed !!
C5 Diag, I had seen your superb video a couple of nights ago. Excellent.
An interesting aspect. I asked a couple of people which single pin (at the relay) would jump straight m to the pump, and both people thought pin 87. It appeared from the internet that a generalisation of simple automobile relays that indeed pin 87 would be the one going straight to the pump. However it is of course (as your video explains) pin 30. Am I right to see this seems slightly odd?
I know you can bridge 30+87 but I was only looking for the single pin to place 12v to. It’s this one people felt sure was the direct contact to the pump, not 30!
Last edited by silver50; Nov 22, 2019 at 09:17 AM.
Thanks for replies. I jumper cabled the pins at the fuel pump relay first and all was quiet. I have now seen that there was however constant 12v at the pump itself. My fuel gauge was slightly erratic going up and down from almost empty to showing an eighth full (if anyone can shed any light on that please do?) so obviously not likely very full so thats good as far as draining is concerned (from the FP housing..). I will see if I can see the earth G401 for the FP. Behind the rear wheel, is it under the splash guard? Having said that my rear lamps were working (and fuel gauge other than it's erratic behavior) so I think the earth will be ok.
Where are you 93 Polo, Ireland? Looks like I can maybe get the carter pump but it's quite expensive.
Is the fuel filter regarded as quite easy to change, it looks like the exhaust is in the way!! Any opinions on the SPECTRA SP6095M from Rock Auto. Rock Auto seem a good place to get parts sent to the UK from but unlike everything else they're only offering two pumps!
I am in Georgia(USA), the avatar goes back a long time on this forum. We went with Carter as it was cheaper than what our guy at the dealership could get for us from GM with wholesale pricing. He also said Carter was an OE supplier for various parts, and that he'd go with the Carter. It is nice having a car buddy that works selling parts at a dealer. The Carter went back in with no custom work, just plug and play.
The filter isn't terrible. The quick release connections can be fun on both of these jobs, coming off quickly or taking some messing with, but they are not hard to get to.
I am not sure if my friend purchased the pump from Amazon or Summit. Summit Racing and Jegs should ship international.
Pin 87 is your "load side feed" and that terminal is fed 12 volts through the fuel pump fuse...pin 30 is the terminal that goes to the pump harness pin A (gray wire). if you jump pin 87 to 30 the pump should operate...if not the G401 will have to be checked...like I had said jumping 12 volts and a separate good ground directly to the pump should tell you if the pump is bad or not !!...you would apply 12 volts at pin 30 to operate the pump but jumping pins 87 to 30 is the easiest way to check the feed side of the circuit....you have 12 volts right there at the relay !!
Pin 87 is your "load side feed" and that terminal is fed 12 volts through the fuel pump fuse...pin 30 is the terminal that goes to the pump harness pin A (gray wire). if you jump pin 87 to 30 the pump should operate...if not the G401 will have to be checked...like I had said jumping 12 volts and a separate good ground directly to the pump should tell you if the pump is bad or not !!...you would apply 12 volts at pin 30 to operate the pump but jumping pins 87 to 30 is the easiest way to check the feed side of the circuit....you have 12 volts right there at the relay !!
thanks. I’ve no battery connected so was only after pin 30. Just others guided me to use 87. Your video was a massive help all round for my checking.
So, live update. See my earth. No matter how hard I tried, I couldn’t even loosen the 10mm nut. Bolt snapping was about inevitable but no biggie. Complete corrosion on contact so fingers crossed my pump might be ok. I’m just about to drill and self tapper a new earth point.
Last edited by silver50; Nov 22, 2019 at 09:59 AM.
WOW !!...if you can't remove the remaining bolt yes just drill a new bolt hole...I'd suggest cutting that eye terminal off and installing a new one...sand off the frame rail to clean metal....an RTV sealant would be a good idea to put over the ground to keep moisture out !!!
Aw man that was disappointing. Still no fuel pump. I ground back the frame with a dremel, cleaned the contact and self tappered it on.
Bah!
As a final check I took power and earth directly to the pins at the pump and still nothing. Looks 100% like a new pump is required. I suppose I was aware items were operating yesterday like the tank sender and rear lights etc so the poor earth was working.
Last edited by silver50; Nov 22, 2019 at 11:00 AM.
Question ??....do you know for sure that there is no break in the wire between your new eye terminal and the harness end ??...don't assume that wire is good !!
I just thought we should go back to this for a second for the benefit of others and my curiosity. Everything I read pointed to this being the universal pin functionality (see diagram) of a basic automotive relay: Pin 87 looks like the pin you would directly put 12v to to reach your chosen item. I'm not talking about bridging, just putting a single 12v source to something.
In my case to try and activate the fuel pump. C5Diag is absolutely right that in the case of the Corvette C5 you need to power up pin the location pin 30on the relay goes to. Is this not unusual? Until I saw the video above made by C5Diag I kept going to pin 87 expecting the pump to fire up.
Last edited by silver50; Nov 22, 2019 at 01:47 PM.
You just have to remember that every relay has 2 power feeds...a control and a load...and as you can see in my video thumbnail the relay is marked with a diagram and the bottom of the relay has the pins numbered...now on different vehicles 87 may not be the load feed as in your diagram...if the relay is not marked just get out your test light and start testing !!...well it looks like your pump is bad if you jumped directly to the pump and it didn't run !!
I'm still looking at new pumps. I am unsure if the Spectra Premium SP6095M pump/sender I can get does or does not come with a new sealing gasket for the tank.
I even see that there were two different sealing gaskets, a G4 and a G25? Some people saying the gasket from GM comes with new tank securing bolts?
Can someone help guide me on this please for my 99MY car to help me order the correct parts? I still don't know whether to go for a new pump only or all in one sender/pump. Am I right C5's have two fuel level senders at both sides of the tank, how does that work?
Last edited by silver50; Nov 24, 2019 at 12:14 PM.
Fuel pump advice please
Aw man that was disappointing. Still no fuel pump. I ground back the frame with a dremel, cleaned the contact and self tappered it on.
