Dies when stopping

[Gibbie1233]

I have a 1980 D50. I recently swapped the 2.6L g54b motor into it. It has a weber carb, electric fuel pump, balance shaft delete, and jet valve delete. Aside from that, the it is stock. It ran for several months after the swap, but now dies whenever I slow down. It does not matter if I am in gear or neutral, it will die anyways. It runs perfectly fine otherwise. Giving it a little gas while braking keeps it alive. I've redone spark plugs and wires, redone the entire fuel system, and swapped out the brake booster but I cannot seem to fix the problem. Any advice?

[Gibbie1233]

I've also replaced the choke, and when it is engaged, it does not want to die as much.

[Gibbie1233]

I have a 1980 D50. I recently swapped the 2.6L g54b motor into it. It has a weber carb, electric fuel pump, balance shaft delete, and jet valve delete. Aside from that, the it is stock.

It ran for several months after the swap, but now dies whenever I slow down. It does not matter if I am in gear or neutral, it will die anyways.

I've also replaced the choke, and when it is engaged, it does not want to die as much. It runs perfectly fine otherwise. Giving it a little gas while braking keeps it alive. I've redone spark plugs and wires, redone the entire fuel system, and swapped out the brake booster but I cannot seem to fix the problem. Any advice?

[camoit]

How many PSI is the pump putting out? 3PSI.
After that look at the float level.
If the bowl is toward the front of the truck it will need to come up 1/8".
When the fuel sloshes forward it starves the carb. If the float is on the back side of the carb it goes rich when sloshing forward.

[camoit]

How many PSI is the pump putting out? 3PSI.
After that look at the float level.
If the bowl is toward the front of the truck it will need to come up 1/8".
When the fuel sloshes forward it starves the carb. If the float is on the back side of the carb it goes rich when sloshing forward.

[SubGothius]

Common issue with a Weber swap where the carb is mounted with the fuel float bowl towards the rear -- as typical for a Weber DGEV, which is most easily installed in our trucks with this orientation.

Under hard braking (or going steeply downhill), inertia (or gravity) causes fuel from the bowl to slosh forward into the fuel jets, causing a rich condition that can induce stumbling/stalling. Likewise, under hard acceleration (or going steeply uphill), inertia (or gravity) causes fuel to slosh backwards, starving the jets somewhat and causing a lean condition that can induce misfires or reduced power. Braking gently far in advance of a stop whenever possible, and perhaps raising the idle slightly, can help mitigate this somewhat.

However, mounting any carb with the fuel bowl in front is preferred, as this leads to the opposite of the above -- hard braking and going steeply downhill induces a slight lean condition, and acceleration and going steeply uphill induces a slight rich condition.

The Weber DFEV is basically a mirror-image of the DGEV and easy to mount bowl-in-front with stock throttle cable routing, tho' it's harder to find and thus tends to be more expensive. The Weber DGEV can be turned around to put the bowl in front, but this requires some creativity with throttle cable routing to have it approach the carb from the intake/battery side of the engine, such as flipping over the cable bracket/guide at the firewall and bending it slightly to help the cable housing clear the brake booster and master cylinder.

[RCY1989]

Common issue with a Weber swap where the carb is mounted with the fuel float bowl towards the rear -- as typical for a Weber DGEV, which is most easily installed in our trucks with this orientation.

Under hard braking (or going steeply downhill), inertia (or gravity) causes fuel from the bowl to slosh forward into the fuel jets, causing a rich condition that can induce stumbling/stalling. Likewise, under hard acceleration (or going steeply uphill), inertia (or gravity) causes fuel to slosh backwards, starving the jets somewhat and causing a lean condition that can induce misfires or reduced power. Braking gently far in advance of a stop whenever possible, and perhaps raising the idle slightly, can help mitigate this somewhat.

However, mounting any carb with the fuel bowl in front is preferred, as this leads to the opposite of the above -- hard braking and going steeply downhill induces a slight lean condition, and acceleration and going steeply uphill induces a slight rich condition.

The Weber DFEV is basically a mirror-image of the DGEV and easy to mount bowl-in-front with stock throttle cable routing, tho' it's harder to find and thus tends to be more expensive. The Weber DGEV can be turned around to put the bowl in front, but this requires some creativity with throttle cable routing to have it approach the carb from the intake/battery side of the engine, such as flipping over the cable bracket/guide at the firewall and bending it slightly to help the cable housing clear the brake booster and master cylinder.

great explanation!!! I have always wondered about this!!