4.8 Fuel issues and wix corvette filter
Thread Starter
Staging Lane
Joined: Aug 2011
Posts: 93
Likes: 0
4.8 Fuel issues and wix corvette filter 4.8 2008 LY2 in a Jeep TJ been running about two years and 10k miles went to upgrade pump to a walbro to help with fuel starving at WOT
I hooked up the wix corvette filter regulator as so many threads indicated . And originally I used the stock fuel pump Tj , It ran ok and is what is below in the pressure test . BUT when I recently installed the newer higher volume walbro pump it did run great for about two tanks worth. Im thinking either I have a crappy knockoff walbro and its failing to build enough pressure to trigger the return to function properly as I am getting NO return flow at ALL. Soooo if I understand how the walbro works it HAS to have return flow to stay cool. And if Im getting no return then thats is whats causing the bouncing pressure at idle but runs better with rpm , because at idle the pump is deadheading and at rpm its free flowing. I setup a test tonight and bench ran the pump to the filter with the return just open to the air . I then would pinch off the feed line engine output side of the filter regulator , If I understand this filter regulator it should pour fuel out the return at this point. Its a new filter and I tried two pumps, the new walbro and the original stock jeep pump . Im thinking the whole time the stock jeep pump has beeen running for two years it has NEVER been dumping return as it cant produce enough pressure to cause it to dump back . It must not be as susceptible to overheating as the walbro so it never failed.
The problem is I am at a loss as what to fix . Order ANOTHER walbro (not knockoff) is only thing I know to do .
On the filter its hooked up the end with two lines , the larger line is feed from pump and smaller one is return , the other end of filter engine side
like this picture http://www.hotwireauto.com/webi…/99_...uel_Filter.jpg
Is the pinch off method a valid test of the pump and if the regulator is working ?
Thanks
Lowell
I hooked up the wix corvette filter regulator as so many threads indicated . And originally I used the stock fuel pump Tj , It ran ok and is what is below in the pressure test . BUT when I recently installed the newer higher volume walbro pump it did run great for about two tanks worth. Im thinking either I have a crappy knockoff walbro and its failing to build enough pressure to trigger the return to function properly as I am getting NO return flow at ALL. Soooo if I understand how the walbro works it HAS to have return flow to stay cool. And if Im getting no return then thats is whats causing the bouncing pressure at idle but runs better with rpm , because at idle the pump is deadheading and at rpm its free flowing. I setup a test tonight and bench ran the pump to the filter with the return just open to the air . I then would pinch off the feed line engine output side of the filter regulator , If I understand this filter regulator it should pour fuel out the return at this point. Its a new filter and I tried two pumps, the new walbro and the original stock jeep pump . Im thinking the whole time the stock jeep pump has beeen running for two years it has NEVER been dumping return as it cant produce enough pressure to cause it to dump back . It must not be as susceptible to overheating as the walbro so it never failed.
The problem is I am at a loss as what to fix . Order ANOTHER walbro (not knockoff) is only thing I know to do .
On the filter its hooked up the end with two lines , the larger line is feed from pump and smaller one is return , the other end of filter engine side
like this picture http://www.hotwireauto.com/webi…/99_...uel_Filter.jpg
Is the pinch off method a valid test of the pump and if the regulator is working ?
Thanks
Lowell
TECH Fanatic
Joined: Jun 2014
Posts: 1,533
Likes: 12
I have the walbro 340lph with corvette filter and I can hear it return to tank when I'm low on gas. It's a filter /reg . Maybe pump is not pushing enough to get over the 58psi to be able to return. I would look at 12v lead is the wire thick enough? How is your ground? When I put in my set up , racetronix had a big write up on power requirements and how too small a lead will result i low fuel pressure at wot
